There are controllers that split in half and you stick the phone in the middle for a Switch-like form factor. The ergonomics are much better than the controller

There are controllers that split in half and you stick the phone in the middle for a Switch-like form factor. The ergonomics are much better than the controller clips because those end up being very top heavy with most newer phones. The real problem is that there are few mobile games designed for controllers, unless you want to use one of the streaming services or console emulators.