Answering my own question. I’ve had problems with LO being VERY slow to open.
It opened fine in safe mode, but when started normally I got a splash screen, then a period of 20 - 40 seconds when it stalled, and was not even showing in task manager.
Finally it opened with thumbnails of recent files. I tried deleting some that were no longer valid - and it crashed.
I didnt want to delete my user profile as there are settings that suit the way I work.
I changed the file history size from the default down to 8 following instructions here (its hardly obvious!)
Now it opens almost instantly.