What happened? How did it happen
When using thirdparty native autofill (Strongbox Passwordmanager) with macOS Tahoe the sceen flashes shortly but nothing pops up. What I can say however, is that this worked flawlessly on the previous macOS version.
What are the steps to replicate the issue (from a new clean Orion profile, if applicable)?
Click on Password Providers, then Strongbox when signing in somewhere.
Does it happen in Safari (if it could be a WebKit bug)?
This does not happen in Safari.

I belive native autofill requires a premium subscription for Strongbox, so this is not really accessible to reproduce.
The Dialog of Strongbox to pop up.
0.99.137-beta
Tahoe (26)