Hey @all,
I just stumbled over free and open source Bulwark web client which actually works very well.
It is a pure JMAP Client for mail, contacts, calendar and more. It is focussed on Stalwart and even support it's advanced features.
Running this on my tiny QNAP nas with no issues since a few days. It should be added to the list of clients at
jmap.io.
Cheers,
Chris