Huh, I forgot to write that I even copied the mentioned local profile into my .thunderbird environment without avail, and into my home folder with same results. And I didn't mention that I found the same questions even here: https://support.mozilla.org/en-US/questions/1440794

However, the chosen solution seems to be rather frustration tha a real solution. I've tried it and also killing .parentlock and lock (the latter marked as wrong link in the file system) didn't work.

I fact, I have my mail archives stored in my local folder. It's a pain in the back always being forced to change to windows before mailing or storing anything outside IMAP folders. Actually, it's the first time I'm really happy still having Windows as a working backing system.

Mint is part of the problem. It uses ubuntu as a base and they now use sandboxed snap packaged instead of the older package manager format. ARCH I think.https://ubuntu.com/core/docs/security-and-sandboxing

The already running can be caused by the presence of a parent.lock file in the profile. With Thunderbird closed just delete the file.

Hi Matt,

Thanks for your proposal, but deleting "parent.lock" doesn't work. That's what I've found already in some fora. Before I've deleted even more, e.g. "lock" (a link, marked "faulty" in Linux) and ".parentlock" (0 byte).

Linux Mint 22 doesn't use Snap per default (I think it's installable - I'm not sure). Even more, they have introduced a purely Debian based edition - because of Canonical's own development paths - like Snap. Nonetheless, even being an apt package it might be broken somehow as it seems that the Mint guys are quite involved in some parallel developments concerning their code basis. However, I'll try asking in the Mint environment as well.

Before the last major upgrade of TB I'd been able to access both profiles from Windows and Mint. Both are stored outside the normal Windows environment, on a different drive. Instead of further trying to get access from Linux side, I created a pretty new profile and was able to import almost everything but my local folder.

I'm neither a dev, nor a Linux nerd. Rather a power user and I'm teaching on a voluntary base how to use TB and other useful FOS applications. As far as I can see the local content wasn't touched by the upgrade and is still in the original text format as it was before. It still works fine under Windows. I've even tried to copy it into the ".thunderbird"-folder in Mint, but it doesn't change anything. Linking the path even to this internal location still shows nothing in TB (as before) and the import fails as well.