Thunderbird will provider their PRO services using stalw.art as email backend. I was considering using it too to replace really old mail system in our company. It looked like modern stack using jmap, but it seems thunderbird actually does not support jmap? Or is it only in their PRO extension? Does it mean I cannot use this unless it is with their services? I'm confused.

Of course there is still IMAP, but I hoped for better.