The input method in FLTK doesn't work anymore. It seems that this stopped working in tlclient version 4.10.1. It still works on Windows and macOS. We will probably have to do a workaround to fix this since it has been bug reported to FLTK:
It looks like this change was caused by the upgrade to FLTK 1.3.5 on bug 6116.
Not doing any release notes as FLTK's input methods handling is a bit hit-and-miss on Linux anyway because of the very basic font handling there (you often just get the "missing glyph" marker).
This is now fixed for Linux. Tested with Fedora 31 and tlclient version 6365 and it works fine, and input methods are disabled within the session.
Also tested that input methods still work and is disabled in the session with tlclients on:
✓ Windows 10
✓ macOS 10.15