Upgrade Thunderbird
 

Lately, I've been having a lot of problems with Thunderbird. Finally, I decided to see what version I had. Damn. I think I waited too long; now it won't upgrade. I've been trying to upgrade Version 68.12.0 to Version 115.9.0

Please help.

How are you trying to upgrade. What, exactly, have you tried and what, exact, happened? What errors did you get?

Upgrade Thunderbird
 

I've tried Help -- About Mozilla Thunderbird
I've tried downloading thunderbird-115.9.0.tar.bz2 and running T-bird from there.

...and...
You don't say what you're doing to actually upgrade anything, what command(s) you're running, from where, on what version/distro of Linux, or what (if any) messages you're seeing. Looking at the "About Thunderbird" link won't accomplish anything, and not sure what you're running from a compressed TAR file. If you provide some details we may be able to help.

Thunderbird should be available as a package on a good number of systems, and that .bz2 file has a program called "updater"...did you run it??

Will this work?
I think I will copy my mail from my folder on my MX-19.2 to an installation of Mint Linux on another machine, then copy the whole .thunderbird on Mint and copy it to my MX-19.2 machine. Do you think it will work?

When I copy my old mail folder, which is quite large with hundreds of subfolders, into a new installation of Tbird the version reverts back to 68.12.0.

..and...
You seem to have ignored the questions you were asked previously; is there a reason??

Thanks so much for trying to help, I've tried to answer your questions between your lines below.

You don't say what you're doing to actually upgrade anything,
-----I tried Help--About to see if it would upgrade automatically.

what command(s) you're running,
-----I haven't tried any linux commands in the terminal

from where, on what version/distro of Linux,
----- MX-Linux 19.4 (uname -srm) Linux 4.19.0-26-amd64 x86_64

or what (if any) messages you're seeing. Looking at the "About Thunderbird" link won't accomplish anything, and not sure what you're running from a compressed TAR file. If you provide some details we may be able to help.
----- I renamed .thunderbird, then tried to run it from the following.

Thunderbird should be available as a package on a good number of systems, and that .bz2 file has a program called "updater"...did you run it?
----- I tried unzipping thunderbird-115.10.0.tar.bz2, but I really don't know what I'm doing. I need to learn more.

So, you essentially did nothing. Clicking that does nothing but pull up an info page.
...despite being given the very obvious command noted to you previously that is "updater"??
Since Thunderbird looks for the .thunderbird directory for files/information/configuration, renaming it to something else only means that your program won't see ANYTHING.
If you look in that folder, you'll see files...one of which is a program called "updater". And you are many versions behind Linux-wise...when was the last time you updated? That version hits end-of-life in June.

Would probably be best to back up your data and do a fresh install of everything, because if all your software is as old as that version of Thunderbird, you could do with updates across the board.

You are so right.

I used to pride myself on not being resistant to change.