I have a pine-phone and the virtual keyboard just refuses to pop up for some apps (like firefox!!). I keep looking in the settings for "force virtual keyboard on" or something but can't find it.
There must be some way to make this work on other Plasma Mobile distributions.
[edit]
Can confirm keyboard works in FF on Manjaro, but it has other jankiness (e.g. it seems to think it is much wider than the screen).