Mupdf-gl doesn't seem to react to keyboard events

mupdf-gl seems to run with warnings such as-

warning: This version of MuPDF has been built WITHOUT clipboard or unicode input support!
warning: Please file a complaint with your friendly local distribution manager.
Xlib: sequence lost (0x10000 > 0x59) in reply type 0x7!

It doesn’t respond to any key presses such as f for full page etc.
When I click on an annotation an editor pops up and I can change dropdowns, click buttons etc but if I try to enter text nothing happens.

Does anyone use this successfully?
Does anyone have any ideas what the problem might be an how to fix?

Operating System: Manjaro Linux
KDE Plasma Version: 5.26.4
KDE Frameworks Version: 5.101.0
Qt Version: 5.15.7
Kernel Version: 5.15.85-1-MANJARO (64-bit)
Graphics Platform: X11
Processors: 4 × Intel® Core™ i5-2500K CPU @ 3.30GHz
Memory: 15.6 GiB of RAM
Graphics Processor: NVIDIA GeForce GTX 1060 3GB/PCIe/SSE2

Maybe this bug report is similar:

But it’s from 2018.

This sounds like it could be a reason.
But I can’t see, from the PKGBUILD used to make this package, how this was done, how the unicode support was excluded from the build.

… there is the"normal" package: mupdf
which might be the alternative

I tried both but they seem quite different.
mupdf recognises some keypresses but doesn’t seem to show any details for annotations, doesn’t bring up a file selection window if run without pdf filename …
thanks anyway