SUMMARY
I'm unable to enter non-ASCII text from my android phone to PC. They transmitted text 
1) either don't reach the PC at all
2) either appears in a weird manner, symbol by symbol, like someone is typing it slowly
3) either a few symbols out of the initial string appears

It doesn't happen with ASCII symbols which appear IMMEDIATELY. 

STEPS TO REPRODUCE
1. pair
2. on phone: open KDE Connect > Remote input > Compose send
3. on phone: send "foo bar"
4. on PC: it appears immediately and as a whole
5. on phone: send "привет мир"
6. on PC: it appears symbol by symbol in the best case, or it either gets filtered in that odd way.

For example, if I send this text: "Я помню чудное мгновенье передо мной явилась ты как мимолётное виденье как гений чистой красоты" (a stansa from a Pushkin poem) this is what reaches my PC:
"Я помню веньеп ередомной акгена соты тойкрас от ыто йкрасотыто йкрасот ыто йкрас отытой красоты"

This looks so weird that I cannot even imagine an explanation for such a behaviour :)

SOFTWARE/OS VERSIONS
Operating System: Kubuntu 22.04
KDE Plasma Version: 5.24.7
KDE Frameworks Version: 5.92.0
Qt Version: 5.15.3
Kernel Version: 5.15.0-53-generic (64-bit)
Graphics Platform: X11
Processors: 16 × AMD Ryzen 9 5900HX with Radeon Graphics
Memory: 27.3 GiB of RAM
Graphics Processor: AMD RENOIR

ADDITIONAL INFORMATION
Android: 13