Any othe available options work as the “domain user” which is why “mod_php” was removed since it runs as “apache” or “nobody”…
PHP-FPM is built into the PHP project, so it’s generally the best one to use, while FCGId would be the next best… CGI Wrapper is really a last resort IMHO.
In the entire lifetime of Virtualmin you should have never been using mod_php. We’ve always discouraged its use in favor of other execution modes (FPM today, seuxec+FCGId in the past).
For the past several years, mod_php has been optional, but not installed by default, while we discouraged its use (and the PHP developers discouraged its use, too!). Now, if you’re using mod_php we can’t/won’t help you. It is dangerous and inefficient. There is not reason to use mod_php.
Don’t use mod_php. You don’t need it. It does nothing good for you or your users.