I’m trying to install version 9.01 and get “could not find driver”
I’ve searched te forum and followed advice to overwrite the concrete folder did that to no avail!
The 8.5.x version works for some time but then generates the same error.
I’m at PHP 8.0 other versions of PHP give the same.
I’m at a loss to be sure.

That error normally means that the PHP extension pdo_mysql isn’t enabled.
You’ll either need to contact your host, or check the extensions enabled for PHP in your cPanel/equivalent.

You might also want to stick to PHP7.4 for now. I believe V9 works in version 8 of PHP, but it’s still very new compatibility, so 7.4 is likely to be more stable for the time being.