my guess is filtered dns.
I just audited my system(firefox 110 on openbsd). and when dns is acting up(I disabled external dns leaving only my internal domains resolvable) firefox takes forever to do anything waiting on dns timeouts.
firefox is making requests to
www.google.com #why? I don't have google set as my default search engine.
detectportal.firefox.com
9.9.9.9.https #???? this is strange. DoH? but I should have it disabled.
contile.services.mozilla.com.
firefox.settings.services.mozilla.com.
content-signature-2.cdn.mozilla.net.
push.services.mozilla.com.
And I probably missed a few.
Well, Sigh, I have a new weekend project. poking around in about:config trying to turn this bullshit off off.