install it and find out and report back, given the reviews I have read indicate it is just a half finished reskin of windows 10 optimized for touch on a surface I do not think you will see any issues at all. But I will not be rushing in.

thank you but no I will not make the guinea pig. I expect more precise and serious answer than "test it and we will be happy to know if this crashed your system". So far none of the version available mention any compatibility with Windows 11 in the system requirements...hence my questions.

You could always spin up a virtual machine, install Windows 11 and Thunderbird and see how it goes.Make an effort, put in the work and be a source of helpful info for others. While I tinker with virtual machines a lot, I haven't bothered to even download Windows 11 yet. I just don't see what the rush is for.

Thank you but again no. My question is quite simple...

If yes which version is compatible? If not when approximately a compatible version should be made available?

I have been using Thunderbird 91.2.0 (64 bit) on Windows 11, and it works with a couple of minor glitches. The header pane when composing a message sometimes has a border that overlaps with the to, cc, subject fields. This is only an appearance issue, and it is quite usable. The other is that if I view the source of a message, the windows comes up blank or with a few random characters, but scrolling the window fills in all the data. Annoying, but since scrolling or iconifying/deiconifying fills in the window, it is still usable. This is on Win11 Pro; may be different on home or on other systems. (Was an upgrade on a new system)

A support person replied to me and suggested fixes. The simplest is to turn off hardware acceleration in Preferences/General/Indexing and restart Thunderbird. That fixed both problems.