Hi, thanks!
No, I have a Machine A from which I want to move my .mozilla and .thunderbird settings to Machine B. I copy them to a USB stick, stick that into Machine B and copy (or paste) them into the home directory. It’s worked for years, but now for some reason it doesn’t. I made a screenshot of the directories on the USB because I thought something odd might happen at that point.
The distros on which I copy the settings directories are also pristine, ie I haven’t touched anything on them usually, copying my Firefox settings is pretty much the first thing I do.
Weird.