Hi, for me this workaround works fine:
OPENHAB 2.5.11 - FB 7590 - OS 7.21 Works fine
OPENHAB 3.1.0#2115 - FB 7590 - OS 7.21: Integration of things works, but after reboot of Obenhabian (not FB) only 4 of 12 things are online. Disabeling of a thing with status unknown or online to disabled does not improve the situation. BUT in my case disabeling of remote DECT 440 (from online to disabled, 5 sec) causes, that all things are going to be online. After all thnings online, remote is allowed to enable (going to online) and all things remain online.
(using also MQTT & astro binding)