Defender updates should still happen - it's just that any bugs found in Windows won't get fixed - which could leave the computer vulnerable to threats which exploit such things.I'm on Win 10 but I do have an AV, I note advice in this thread is that I don't need it and when the Sub expires I won't buy again. That said next October Win 10 will no longer be supported so I am presuming Windows Defender won't get updates so as I don't want to upgrade my computers (desktop and 2 laptops that aren't Win 11 compatible) I will need to find another AV?
For me, it's a push to upgrade to a new PC, as my current one can't run Win 11 (without bypassing install checks), and has a 1st gen i5 CPU, so is probably almost 15 years old!