Same problem for me. It is really annoying. All I can do is type my text in Notes and copy/paste or scan text.

I'm not sure anyone from the Apple team is reading this thread. First because it's a Forum, and second because there is already an accepted answer in this thread. I have the same problem in iPadOs 15.6.1 and would really like that problem to be solved, but the bug only appears scarcely so I am unable to produce a reproducible list of steps that lead to the missing keyboard. The steps mentioned by @HighendBark used to reproduce the bug in earlier versions of iPadOs, but now if the iPad has been freshly rebooted it no longer triggers the problem. Can someone with a reproducible recipe file a bug report? I did file a report with the feedback assistant but since I cannot easily reproduce the problem I'm not sure it helps a lot. Also, I'm wondering if it is related to this bug: https://bugs.webkit.org/show_bug.cgi?id=238318