"tmux open terminal failed: not a terminal" in terminal emulators other than mintty

[Kacper Michajlow]

Hi,

I'm not exactly sure who to blame for this issue, but I figured I will ask
you guys. Tmux fails to open in anything else than mintty it seems like. It
works from ssh session, probably because pseudo-tty is allocated, but
except that tmux will fail.

There are multiple reports about that, without solutions:
https://github.com/cmderdev/cmder/issues/453
https://github.com/alacritty/alacritty/issues/1687
https://github.com/zeit/hyper/issues/3608
https://github.com/microsoft/terminal/issues/5132

Do you think we could make it work without using mintty?
If yes, should the changes be made in the Cygwin, tmux or terminal emulator
code?
Any pointer would be good so I can poke others :)

Thanks,
Kacper