During upgrade I have received this message

We were unable to start a PHP session. You will need to contact your host to adjust your PHP configuration before you can continue. The error reported was: session_start(): Failed to read session data: files (path: /var/lib/php/session)

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Help please!

I found this as a solution

chown nginx:nginx /var/opt/rh/rh-php73/lib/php/session -R

You would need to contact your hosting company to resolve that issue, as its an issue with your PHP configuration, as mentioned in the message there.