CoffeeCake

That just means you'll have a dedicated IP address for outbound mail, not that your server's sending IP will be revealed.
We use the regular version with no issues. Make sure you setup SPF & DKIM.

Looking at this link, this is a great example where you can save a lot of money by going with something like AWS. Their Lightsail offering is simplified VPS. Compared to that Nimbus plan you linked to, you could have a better provisioned VPS at $40/month (at least US pricing--you'll need do work out the conversion to Prussian Francs). You can have your instance in Frankfurt, Ireland, London, or Paris if you need something based in Europe.
That would give you 8GB RAM, 2 core processors, 160 GB SSD storage, and 5 TB transfer, well exceeding the allocations for the Nimbus plan you linked to at $105/month.
You'd be able to add CDN at free or very low cost, and could even choose to maintain a separate fully maintained database instance and still come out under what you'd be paying Nimbus.
https://aws.amazon.com/lightsail/pricing/
IPS' cloud is using AWS. I'm sure Jordan's prodding about EU based servers simply means they'd put some instances in those European regions if the interest was worth the bother.

There could be some options:

open links within my community in the same window open links to external sites in a new window

I have used it for some years. I have stopped because their code had responsiveness issues. Another issue was the slow performance at large projects. Self hosted was not enough. Cloud was too expensive. We have changed to Ad Manager. 
The earnings for banner advertisements slowed down though. Paid walls, subscriptions, affiliates, writing and featuring content - this is where we are now 🙃

Generally, I would not recommend using IPS advertisement system to sell impressions. Use duration period (number of days) instead. IPS counts impression like page views. If the ad is placed below the fold and the user never scrolls to see it, IPS would count it nevertheless. Advertisers dislike to pay for ads that were not even displayed. 
If an advertiser has own tracking code, you can use HTML/JS code for the ad to place it, so that he can see in his tracking system the stats.

Having the rank image there period is kinda ugly.  Something I'll def remove if we upgrade to 4.6.  Post profiles in general are really lacking structure and it's not cohesive at all in the style.  For example on this website, you have rather large blurry rank images on top of small circular profile photos, the contributor image has weird capsule shading, the Invision Staff image looks like someone randomly screenshotted a logo from somewhere else, and the client pips... The staff badge is also kinda useless since there are multiple other visual cues that make it obvious someone is staff.
First impression is that a handful of people all had very different ideas and someone allowed them all to contribute one thing each to make them happy.  🤣  Unless they reorganize some things or maybe even make the profile photo larger, it all just looks like clutter to me.  I've heavily edited my postcontainer template to get rid of the everything-center approach.

After converting our community to 4.5, we received almost unanimous feedback that the moving of these links was a crime against humanity. I'll be posting a free plugin on the Marketplace that restores all that is right in the world.

Absolutely agree. /summon @Jordan Invision

That just means you'll have a dedicated IP address for outbound mail, not that your server's sending IP will be revealed.
We use the regular version with no issues. Make sure you setup SPF & DKIM.

What do you mean by several mailboxes?
A few folks here use Amazon AWS e-mail services via SMTP.

Those functions are rarely needed and very dangerous.
You are putting electrical tape over the check engine light on your car, and then complaining that the light is the defect instead of the oil leak. Or putting the anal probe directly into the interstellar mouth socket. One of those.
Installing some other software on the same server is not resolving your problem. Other software may not do you the courtesy of warning you that there is a problem, but the problem is global to all PHP based applications.
You seem to think because your other car doesn't come equipped with air bags that a new one with air bags obviously has a terrible defect that makes it crash spontaneously into walls. So you'll drive the old one because that's safer....

Ah! Yes, this message is a warning to you that your server's PHP configuration is unnecessarily vulnerable to being used by individuals and/or organizations looking to exploit and hack your site. Why? Well, most obviously, for alien mind control purposes. It's the only conclusion that makes sense.

The functions that are called out are not at all used by IPS and are incredibly dangerous to leave enabled. It is a security best practice that you should absolutely ensure you're heeding the advice of. They are commonly used to infiltrate web sites and steal data or worse.
If your host does not have the ability to modify your PHP configuration for you to disable those functions, my recommendation would be that you find another host. IPS will work just fine with the functions enabled, yet the warning is there for you as an administrator to remind you that you have left unnecessary risk in your install.
You may be able to disable functions using the php_value stanza in an .htaccess file, yet I would strongly advise you to disable this from your php configuration file. If you are using cPanel or the like, I'm sure there's a mechanism to do this. You want a web host where you at the very least are running in a chrooted environment and have the ability to modify the configuration of your PHP instance in a manner that does not affect others using the same web host or server.

Look, @Daniel F..... we have to admit defeat. AlienOrigins obviously knows we're deep in the pockets with big PHP and have never touched this stuff in our lives. We are no match for his deductive reasoning skills.

It's totally still there. Good luck.

Maybe this?
Did you report an issue via support? What did they say?

You would need to provide details from PHP's error logging to determine what went wrong and what the appropriate solution would be.
The two most likely culprits are:
Necessary PHP extensions that are not installed on your server Insufficient allocation of memory to PHP on your server Your server error message log will tell you which is the problem.
To answer your question, neither the extensions required have been reduced, nor has the memory footprint of IPS been reduced. If your host is underpowered for IPS and you cannot change hosting providers or increase the amount of resources allocated to your site, IPS may not be the best fit for you.
You may want to consider IPS' Cloud offering if server administration is something you're not interested in.

You could get from New York to Los Angeles much faster if you flew a plane as compared to driving a car, however buying a plane and attempting to fly it would be a dangerous enterprise if you only know how to drive a car.
First step is to get a pilots license. Educate yourself on what's needed to know about the more administrative bits of having that level of control and responsibility over a publicly accessible system compared to a managed shared hosting plan. I'd recommend to someone entering this arena today to look at the large cloud services providers. I have no idea what a Nimbus is, yet I'm certain you could provision yourself with computing and memory power in excess of their offerings at any of the large cloud services (AWS, Azure, GCP, DO, Linode, etc.) for significantly less. You will likely fair better at a cloud service once you exceed a basic local business level Wordpress type site.
The other direction to look at is considering IPS' managed service. If you are someone that just wants to focus on running your community and not be bothered by the underlying technologies, this is a way to pay someone else to do it for you.
I cannot even begin to imagine a legitimate use for any of those functions--they all surround running server-side executables. /summon Kier. What the heck?

Absolutely agree. /summon @Jordan Invision

Hello there!
The main purpose of user profiles is to make discovering user's content easier. I've found a way to improve the process a bit.
1. Content discovery
Let's take a look on my profile and especially on the filtering options:

Problem: It's quite a long list that grows with every new app or a content type. I find it confusing as during my time here I've posted only a topic and some posts.
I don't think I'm able to post anything in the documentation, release notes, providers, guides, IPS Blog etc. But I'm still able to filter my results by those options [basically to get no results note].
Solution: The idea is to hide all the empty-result-filters. Thanks to this we exactly know what type of content certain user posted, and save our time on scanning the long list.

2. Reputation view
I wanted to check my reputaion activity and this happened:

Problem: The page shows no results. Quite confusing as the sidebar clearly shows that I do have reputation activity. This is because by default the resulsts are filtered by Status updates in which I have no activity. And the list of possible filters is also very long (as stated above).
Solution:  As we have All activity filter in user's content page by default, we should also have All reputation activity filter in user's reputation page. And limiting the possible filters would (as above) make the experience more intuitive and clear.
In my case it would look like this as I have reputation activity in blog entries, blog comments and posts:

Thanks for reading! 🙂

You do not need to move the file to require http authentication. Simply create a Files rule within your IPS directory that the file requires authentication.
Assuming Apache and that you're not a CIC customer, something like the following should work:
<Directory /var/www/html> <Files sitemap.php> AuthType basic AuthName "Protected Super Secret SiteMap" AuthUserFile /path/to/.htpasswd Require valid-user </Files> <!-- Include everything else you had in here --> </Directory>  

No idea. The logs should help reveal what's going on.