CoffeeCake

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

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.

...
Analytics solutions aren't intrusion detection systems. If you need something that's looking for suspicious behavior, that solution should be ingesting your web server's logs or, more ideally, sit in front of your web server via something like a firewall and use things like inspection.
Matomo and Google Analytics are simply tools that help you understand your audience. You can only control the software running on your services and cannot force any user or robot to run software client side.

Badges already support this - when you create the rule that awards the badge, you can enter a member-facing summary of the rule, e.g. "You posted 50 replies!".

Sorry, just looked at your profile, @AlienOrigins. I realized I forgot a third, equally plausible factor that may be resulting in the error you're seeing.
Yeti in the server.

Busted.

It's totally still there. Good luck.

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.

Sorry, just looked at your profile, @AlienOrigins. I realized I forgot a third, equally plausible factor that may be resulting in the error you're seeing.
Yeti in the server.

Busted.

It's totally still there. Good luck.

Will there be anything for the mobile viewing? Or are we to limited on space?

It'd be great if there were an option for announcements to be pushed out as notifications to specific user groups (as in the little bell notifications, rather than a box above the forum/sidebar as it currently is).
Not sure if there is a reason this isn't included, but I'm sure many people would have uses for this.  🙂 

If the bug tracker is any indication, you need client testing before it will be ready for production.
What's the plan for releasing alpha/beta releases for testing purposes to self-hosted clients?
We're not particularly interested in achievements and will likely not activate them in our community, however speaking from a 4.6 release as a whole the changes look like they would benefit from testing code revisions and third-party integrations.

Yes, find reputable and recognized places for knowledge, just as you'd search for any other product or service online. 🙂
Depending on your learning style, seek out paid or free training/courses from reputable providers (consider looking into MOOCs) or go straight to the source for documentation:
PHP: https://www.php.net/docs.php MySQL: https://dev.mysql.com/doc/ Javascript: https://developer.mozilla.org/en-US/docs/Web/JavaScript HTML/CSS: https://www.w3.org/standards/webdesign/htmlcss

Things look a bit different this time around. With 4.5, there was the "alpha" domain hosted site, then there was a series of beta releases, followed by full releases that may as well have been beta releases. It didn't go as smoothly as maybe would be ideal.
So I'm wondering if we take our lessons learned, and have adjusted things perhaps, what the plan this time is for 4.6.

Invision (broadly) uses five languages:
Front End - things that run in the context of a user's browser:
JavaScript (often in the form of reusable libraries) CSS (Cascading Style Sheets) HTML (HyperText Markup Language) - all web sites use this, and Backend - things that run on a server:
PHP -- what actually runs on the server In addition, SQL is used through extraction layers in PHP via MySQL (or its swap in, MariaDB).  
You will also find some use of JSON and XML. And you will find interactions with other technologies via PHP such as elasticsearch and Redis.
Your ability to establish working proficiency in any of these and then to develop an understanding of the existing codebase is an exercise we can only speculate about. I'd recommend looking for open, free courses that touch on the basics of PHP and front-end web development and see for yourself your ability to pick things up. Many of us have no formal education on these things and have largely taught ourselves. Many of us have formal education in one or more of these areas.
If you have the desire and drive, you're most of the way there.

The hostname of the link you posted contains an underscore. Underscores are not supposed to be used in hostnames and violate the RFCs for valid hostnames. My guess would be that CKEditor is doing something with this link.
Posting it here as a test. Test link

Looks like the same behavior happens here. You should encourage whoever administers that site to consider a hyphen instead of an underscore. In other words, dev-tc instead of dev_tc.

The hostname of the link you posted contains an underscore. Underscores are not supposed to be used in hostnames and violate the RFCs for valid hostnames. My guess would be that CKEditor is doing something with this link.
Posting it here as a test. Test link

Practically every allocated resource and configuration on your server(s), your community's usage of various features, resources allocated/consumed by the various services and tools powering your community, your community's guest to member ratio, and the design and architecture of your server(s) setup.

These are decisions that require a technical understanding and cannot be realistically answered within the scope of a post here. Depending on a multitude of factors, the best choice may vary and IPS gives flexibility in that regard.
If you don't understand something, don't use it until you do.
If you do not have the personal time or skillset to seek out and obtain an understanding of these things, then consider hiring someone who does:
https://invisioncommunity.com/third-party/providers/

This is all you need:

I'm sorry, would you please repeat?

I thought you were asking for the ability to introduce end-to-end encryption on content on publicly viewable content, so that those without the password see encrypted gobbly gook, yet with the password, a person can see the deciphered text.
What is the use case for this? What problem are you trying to solve?
If it's to limit who can see something, why not control that with permissions at the container level?
If it's to encrypt things in transit, why not use SSL and database encryption?