Yeah that's an option but I can't stand Cygwin UX. tmux and mosh for native Windows would both be awesome.
Or compile it yourself using MinGW64 : after installing from msys2.org, pacman -S base-devel etc
It works fine here. I have a Windows Terminal settings to start sixel-tmux instead of bash, using script to provide a pty: just have the command line be:
C:/msys64/usr/bin/env.exe MSYS=winsymlinks:nativestrict MSYSTEM=MSYS /usr/bin/script -c /usr/bin/tmux /dev/null
It's due to a cygwin and how /dev/cons* are different from /dev/pty* cf https://cygwin.com/pipermail/cygwin/2020-May/244878.html
I've tried to explain that a bit better in server-client.c (check line 251) to give the user a clue of what's happening with *cause = xstrdup(c->ttyname)
Unfortunately, even in 2021, properly configuring a terminal can be complicated.
That's why sixel-tmux page has a step-by-step configuration guide, and why I often provide config files in other projects like https://github.com/csdvrx/indent-rainbow : if needed, check https://github.com/csdvrx/indent-rainbow/blob/main/config/wi... even if I need to update it that should give you a good base to start tweaking from.
I strongly encourage you to check your configuration with the steps suggest on the sixel-tmux page, or at least the minimal set of steps shown in http://github.com/csdvrx/sixel-testsuite (which I should update to show how font change should work, with sixels being resize to be kept in perfect alignment with the text, as done in mintty, as several people seem to believe it's a sixel limitation)