Addendum - This problem started with the update to 136.0. Both computers were not doing this prior to the update to 136.0 and both computers are asking for my primary password (twice) when I start Firefox. Hitting the Escape key twice removes the password request. I consider this a bug.

I have the same problem since a few days:

• Firefox asks for my primary password on startup.
• If I cancel the dialog, the dialog closes and directly opens again.
• If I enter my password in the first dialog, the second dialog doesn't appear.

More info:

• I can't pinpoint exactly when the problem started, but it could be since the update from 135.0.1 to 136.0.
• I don't use Sync, I'm not even logged in to my firefox account.
• I am on Windows 11, with no additional antivirus software installed (just Microsoft Defender)
• This still happens after disabling and re-enabling the primary password as described here.
• about:studies seems fine (there was some "studies"-hotfix that caused a similar problem in 2019).
• in about:config, security.enterprise_roots.enabled is set to true, but setting it to false makes no difference (seemed to solve the problem for some people a few years back as well).
• This also happens in troubleshoot mode.
• This also happens when all browser extensions are disabled.

Probably it's bug 1946121.