Ho.

As fist step as Joomla Investigator - enable that:

Then check from where you have error, which file(s) is on table location 1 and 2

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/site1/libraries/src/Uri/Uri.php on line 143

Also that message doesn't help :/ too short !!

Switch to PHP 8.0 and test again.

Have you updated all extensions and template to new version? If you are not sure, check one by one.