@boebbele
Glad you solved it.
I learned there was a homeassistant matrix integration by reading your post and tried it bit could not make it work, I always have an authentication error.
Did you use the core integration or did you use one from hacs?
Also do you use matrix.org or a custom matrix server?
@tifriis
Definitely a good read it’s a nice gathering of tips spread otherwise all over the place