Try create section in project type board, with “ąęć” in name. You will get section with “aec” instead. Try create section with “ó” in name, you will get server 500 in response.
I don’t see any problem with Polish diacritical characters in section, task, subtask names, descriptions & comments using Edge on W 10.
No. Using website.
Greek characters supported for sure. And other alphabets in utf8. Check your encoding.
You are right. PowerShell has some glitches in this matter.