Mac Mini Mac OS Mojave Safari apple id still work?
having problems connecting with
Mac Mini Mac OS Mojave Safari apple id
apple id server does not like Safari 14.1.2 anymore?
this is from firefox
Earlier Mac models
The Apple ID still works, what doesn't work is the web browser. Mojave is fairly outdated now and as such insecure which means Safari is also insecure and may have issues with Apple's websites that require more security that it supports.
Either try to update from Mojave to something newer if your Mac supports it, or use a 3rd party web browser like Firefox yes.
Start planning on upgrading to a newer Mac, as the issues will only be getting worse as the Mac get's older.