For all PHP websites hosted, the default version is 7.3.
I know I can modify the .htaccess to make it use 8.1, but is there a way to set this as default either with SSH or DevilWEB?
.htaccess works recursively, so create a .htaccess file with a PHP version change in the ~/domains/ directory. You can edit/create the .htaccess file via SSH. The help page also indicates how to set the PHP version for PHP CLI.
Alright, I didn't know I could put a .htaccess file in ~/domains/, so this should work!