Steveowitz,
Sorry for the delay, but if you look above in one of my responses, I have identified how to go about retrieving the older messages.
Ah...here it is...from 18Dec2020:
Dec 18, 2020 10:31 PM in response to steveowitz
Okay,
I just opened my Time Machine, and I was able to view & download the archive folder my current desktop.
The messages file extension is .ichat, and I wonder if anyone has been able to open these files in any program OTHER THAN iMessage? MS Word just gives a lot of character strings along with the texts, so this is a tough sell. But, if another program can open and read them, then this may be one way to archive the older (pre-Big Sur) messages.
But as far as from November onward, I have no idea.
For what it's worth, my archive folder is empty, but its last modified date was 15Nov2020 at 4:21.
Cheers!
-Merlin