I found it is also possible to run the older 4.1.3 version of the addon with openhab 4.4 if you do not need access to the new functionality; details here: [OpenWebNet/BTicino] Problems sind OH 4.2 - #19 by mavnn
Obviously this isn’t a “fix”, but it does at least allow people with a MHS1 to continue using the latest version of openhab for everything else while the problem is addressed.