I asked 2 Sunsynk 'master installers' for
#solar quotes; neither of them want to do synsynk. The one I spoke to on the phone earlier offered me a bunch of others and is sending me a quote; the one that came to visit on Tuesday just sent a quote for a Solis based system. Solis does look OK for Home-assistant from what I can tell.
Hmm.
(I asked for Sunsynk after
@nprofile1q... suggestion and checking their manual which shows it has a nice convenient 9 pin D on the bottom)