Yes, Home Assistant unfortunately doesn’t work with password managers. I use enpass and have the same on Firefox. It seems due to the fact that home assistant used DOM manipulation even for the login screen. Woult like to have this changed for a long time. Solution might be to do external logins with keycloak or authentik. However a solid setup with that would require openId-connect kind a login that seems unsupported as well …
This has been driving me crazy for some time too. While I have experience with Authentic, Keycloak and reverse forward auth proxies I’m tired of doing IT in my free time.