Firefox on Android ( / Preview) is generally terrible with input handling anyway. I still haven't figured out a way to paste into a textbox without removing existing text — long press is required to show the menu, but also selects the last word, and unselecting removes the menu.

>long press is required to show the menu

It's not. Tap on the caret and the menu will show up without selecting anything.

Thank you! This does seem to work intermittently (at least, it didn't work when this text box was empty, but started working once I typed in some text). I guess I'll have to file that in my head as "works inconsistently", but at least it… sometimes works?

Same for FF preview.