MORE INFO: I have two accounts. The other is Workspace with only 2000 emails. The issue only occurs when using the unified Archive, and doesn't seem to occur when going directly to Gmail All Mail. For now, I will have to stop using Unified Folders.

MORE INFO 2: Clicking on Gmail-All Mail directly doesn't cause the interface to freeze, however there is substantial delay in loading email bodies.

I am assuming your account is IMAP. What response to you see when clicking on the gmail all mail folder (that is archive in Google view of the world) Thunderbird will use that folder for archiving even if you try and set it to something else in account settings.

Yes, sorry, IMAP. Thank you for responding.

There are two scenarios:

1. The scenario my OP was about: When I click on Unified Archive (which I know is the All Mail folders for my two Google accounts, personal & Workspace), the interface just freezes for 5+ minutes. There are system error messages (in Linux, it says thunderbird not responding Wait or Force Quit, and in Windows it just says "Not Responding" in window frame). There is no TB error.
2. The second scenario: When I click on All Mail specifically in one of my accounts, the interface stays working, but the body of the first message I click on take about 1 minute to load.

Honestly, the first scenario is the one that matters most. For now, I cannot use Unified Folders.

open your profile folder, then the mail folder. Make sure Thunderbird is simply not running in the background delete the folder "Smart Folders" and restart Thunderbird.

Not saying it will help, but it will force a complete rebuild of the unified view which might clear up something.

OK I can try tomorrow, but this happens immediately on brand new installs, so why rebuilt Unified Folders right after a fresh install?

re : I have changed sync to not keep (or to keep) messages on device. I have lowered sync to 30 days. You would need to compact your folders on a more frequent basis to maintain those settings.

The 'All Mail' is not just the Archive - it is a complete duplicate of every email that exists in that gmail account - incoming, outgoing, archived, so it's not just an archive. So in your case the Unified 'Archive' folder is actually showing you every email in existance. How can you tell which emails are actually archived? There is no means of detecting whether any email in All Mail actually has any labels applied.

As far as gmail is concerned every email lives in the 'All Mail' any way, but if you use 'Archive' then gmail just deleted all the labels, so you cannot see that email without either subscribing to see a very large 'All Mail' or logon to webmail which is what gmail wants all along. It is a very conniving attempt to draw people back to gmail webmail or offer them an unwieldy 'All Mail'.

Suggest you consider the following: I use this method. In gmail imap account - Create a folder called 'Archived', then in 'Account Settings' >'Copies & Folders' set up to use 'Other' and choose 'Archived folder gmail account' in settings. This then applies an 'Archived' label as opposed to a complete removal of all labels. This means it does not matter what gmail do with it, it is still in the 'All Mail' folder because that's where gmail puts everything.

Bottom line is this: You do not need to subscribe to see the 'All Mail'. It has become redundant. You do not have a complete duplicate of all your emails. You really can know that 'Archived' are emails you 'archived'. Files are smaller. Uses less space and runs more smoothly.

Thank you, @Toad-Hall. understand all that about Gmail.

Within a single account, the All Mail folder renders properly, meaning it shows me every email in existence in the account. The expected behavior is that clicking on Unified Archive shows me the combination of every email in existence for both accounts. While this expected behavior does happen, it’s only after a 5+ minute freeze up.

I don’t want to create a real “Archive” folder, and I’m not sure I see the need for this. In my accounts, mail is either Inbox or not, I don’t need an Archive label.

Thunderbird works absolutely properly within each Gmail account (All Mail works just fine.) It should work properly when both are combined in “Unified Archive” (which is basically Unified All Mail, which again I understand to be unified every email.) Instead it freezes.

I’m not sure I see the issue here. All Mail works properly in each account. It should work properly when combined.