There's a built-in option that comes with Android 10 which allows you to lock the screen without using the bottom.
In your phone settings, go to "Accessibility" and enable "accessibility menu".
This will now put an icon on the the right side of your navigation bar. Pressing on the icon will bring up a menu, with one of the options as "lock screen". ...
The app Lock works but a downside is that afterwards the phone cannot be unlocked using a fingerprint, only using the pattern. (Also it is not available from within other apps. So a movement activated solution would be better.)