I am a novice at Linux, but I will share what little that may help. When you copy the Thunderbird folder, one of the primary reasons is that the Thunderbird folder contains a file named profiles.ini. That is a simple text file that tells Thunderbird where the profile is located. If thunderbird starts and sends message that profile not found, it is because that file is either not found, or does not point to the active profile. I suggest looking at a default setup on Linux to see exactly where the components are - the Thunderbird folder, the profiles.ini file, and the profile.

Be sure you're copying the appdata\roaming\thunderbird folder and NOT the appdata\local\thunderbird one.

I am very sure I copied the correct folder. Have done this before but never to a Linux based system.

I am assuming the problem is the Linux version of TB was using ".thunderbird" as its base dir, and the Win10 TB was using "Thunderbird" as its base dir. A simple rename did not work. The Wind dir tree was there, renamed to what the linux version expected, but TB still recreated the dir tree with an empty set of data and asked me to create an acct.

Not sure what else to try. Would moving to a different TB version on Windows be more compatible with the Linux version? Something else?

Ok, let's get to basics.

1. exit thunderbird
2. copy your desired profile into the thunderbird\profile folder alongside the default (active) proflle
3. restart thunderbird
4. click help>troubleshootinginformation
5. scrolll own to 'profiles' an click 'about:profiles'
6. if you see your profile there, see if you can launch it
7. if not, click the 'create profile' button on that screen
8. click next
9. enter a shortcut name first, such as MYPROFILE
10. now, click the 'choose' button and select the profile you placed and launch it

Thanks David. Just gave your sequence a try. Problem is Linux TB does not seem to recognize the old profile tree as a valid profile. It works just fine on Win10, and I copied it when TB was not running. Yet, the Manjaro Linux TB does not ever list the copied old profile in about:profiles.

In following your steps, I did create a new profile, did rename it. However the old copied profile never appeared in the list (and there was no choose button). The newly created/renamed profile became the active one. But still no sign of the old profile in the on screen list.

I suspect this is due to diffs in the file structure/data between the two version of TB. The fact that one had Thunderbird as the upper dir, and the other .thunderbird is perhaps a clue.

Short of comparing the various profile files for differences, is there anything else you can suggest?

OK looks like I have it solved. The .ini file from the Win10 side had the profile dir in the Path=. Looks like that made the old ini file incompatible back when I first moved/copied it over.

So I edited the block from the Win10 ini and copied it over to the Linux ini, taking the dir out of the path and giving it a new [ProfileX] number, and it seems to work. At least as far as I've seen thus far.