@maretval I am facing the same issue. this is an Alpine Linux 3.11 and I have php mysql extension installed and enabled. I checked php_info and looks fine to me.
I used the same host config for hosting other PHP applications with mysql and it works fine.
any thoughts where do check to fix this issue?
I actually fixed this issue - and dont know how ! it was either the ui which didnt allow the drop-down to display or some mingling and restarts that fixed it !
I am facing a different issue now after installation - not allowing me to login and seeing some errors in apache logs