My personal experience of 1Password 6.8.9 is that it does work as in Big Sur.
So, integration with Safari and Brave is broken (haven't yet installed Firefox to test, but its working 1password add-on did allow integration within the browser on Big Sur).
Other points.
(1) I installed Monterey on an external SSD to test. It is still not on my main volume and I won't update that until I have more fully tested from the external drive.
(2) I sync using iCloud and Monterey found my vault straight away. I was able to use both the main app and 1password mini from the menu bar. I haven't tested other methods of syncing as these don't apply to my use case.
Note also this thread in 1password community which also suggests there is functionality even if not all the bells and whistles https://1password.community/discussion/comment/617624
I was trying to decide on upgrading or installing to an external SSD on my 2015 MacBook Pro. I think that I'll just do a clean install as my new MacBook Pro is running fine on it. I plan to give the 2015 MacBook Pro to my wife and it would be best with a clean install. She just does email, web browsing, watching videos. She only recently expressed a desire for a laptop. She has a 2018 mini which she uses most of the time.