To ensure full compatibility for the transfer, you could uninstall 141 completely and install 115 on the new computer from here:

https://ftp.mozilla.org/pub/thunderbird/releases/115.18.0/win64/en-US/   

Here is the link for moving a profile in Windows when installed in default location:

https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer

here is the info in brief steps:

1. ensure thunderbird is NOT running on old machine
2. enter %appdata% in search window on task bar and press Enter key
3. this should open windows file explorer in Appdata\roaming folder
4. highlight the Thunderbird folder and copy to external media
5. ensure thunderbird is installed on second computer and NOT running
6. enter %appdata% in search window on task bar and press Enter key
7. you should be in Appdata\roaming folder , copy&paste the exported Thunderbird folder there. This may prompt to overwrite an existing folder of same name. allow it
8. start thunderbird and all should be there

That 'identical' reference

David, Thanks for your prompt reply. Presumably, after I install 115.8.0 version on the new Windows 11 computer and do the email transfer then Thunderbird will automatically update the new computer version to the most current version for Windows 11 - is that correct?

Also, I'm not a Thunderbird expert so maybe you can tell me, when I do the Appdata\roaming folder transfer to the new computer does that transfer set up the same Thunderbird connection to my email service (AOL)? That is, does all the port info, usernames, passwords that my old Thunderbird used to reach my AOL mail automatically carry over to the new computer so that I don't have to do all that again? Does my question make sense? - Chris

on first question, no. you will have click the update button on second question, the transfer is 100% - all data and account settings and passwords are transferred. Some email providers require setting new passwords for a different computer, but I don't think AOL has that requirement.

After I transfer my Thunderbird folder via Appsdata copy to my new computer with the identical old version 115.18.0 and then do an update to the current version, what happens to my email/folders/contacts/organization etc? Will the old email/folder layout from 115.18.0 be preserved in the current version? Will anything be changed/rearranged or will it pretty much look the same?

it should be identical, other than new features of latest version.

A couple problems. The link you gave me to version 115.18.0 has two files - an exe and an msi. Which do I select? Either one, after I select to install, does the install and then opens a frame "Set Up Your Existing Email Address." I thought I didn't need to do that.

Also, when I copied the Thunderbird Appdata to my new computer Appdata/roaming I got a message that three of the files (.ini) already existed in the roaming and asked which three I wanted to keep. I selected the files that came from the old Thunderbird.

When I open the 115.18.0 on the new computer after I copied in Thunderbird Appdata nothing appears in Thunderbird on the new computer. I'm stuck.

David - All problems solved. Looks like the transfer has gone fine. Thanks very much for your help. - Chris

Good to know. I'm glad that it went well.