I have found that when I open Edit; Settings in said version of Firefox I see this link at the top of each page
The link takes me to about:policies and shows the Policy Name DisableAppUpdate set to true. This is a personal computer, no organization. I have also found:Your browser is being managed by your organization.
The same version of FF on Ubuntu Mate 20.04 does not show this link.
A freshly installed Mint Mate 20.2 loads FF 89.0.2 which does not have the link. Upgrading FF to 96.0 causes the link to appear.
The FF community discussion about this issue talks about Windows, changing registry entries, blaming some anti-malware software etc. Nothing about Linux.
I have not yet come across any negative impact from this. Still, as this link does not appear in Ubuntu it smells like a Mint issue to me. Any ideas?
TIA,
Ken
p.s. After updating to FF 96.0 I observer that the "It looks like you haven't started Firefox in a while... [Refresh Firefox] message appears each time I start it. Refresh hoses a bunch of things. I think there is a way to disable this message but I have not found it. I think I need to try it on a test machine and see if it makes the offending managed by your organization thing go away.