My usually reliable Cube forgot its settings for the second time in a few months so I decided it was time to flash the RFBee I have been keeping ready
All very straightforward with instructions at https://github.com/cgommel/culfw/blob/master/culfw/Devices/RFbee/README (https://github.com/cgommel/culfw/blob/master/culfw/Devices/RFbee/README)
The changeover procedure is documented (in English) at http://www.fhemwiki.de/wiki/MAX!CubeMigrationToFhem (http://www.fhemwiki.de/wiki/MAX!CubeMigrationToFhem)
Again straightforward except for one window sensor that I think must have died. A spare came up OK
Thanks to the CULFW developers and the author of the wiki article