My workplace allows me to use a Mac, but doesn't have much experience with them; their support is minimal if well intentioned, and generally as much harm as help. This includes installing antivirus software etc.
Recently, both Safari and Chrome have started showing the "This connection is not private" error with most off-site URLs. This is a recent change, and includes web sites I was able to access last week. I'm running MacOS 10.14.6 (18G87) with all updates.
This isn't a question of our IT deliberately blocking sites, as I can access them from my Windows computer (and in any case it includes sites that are clearly work-related).
In some cases, but not all, I'm able to bypass the warning by following the accepted answer for How do I bypass "this connection is not private" warnings in safari? (i.e. clicking through the "show details" buttons and entering my password), but this doesn't always work, and is pretty inconvenient besides.
I've also tried the other answers from that question, but these do not work. This is perhaps not surprising as that question refers to development work which involves self-generated SSL certificates, and my situation doesn't involve these.
I've also tried turning off antivirus software (insert scare quotes as you like), and that didn't help.
Note: When I look at the certificates on the problematic sites, I see the site's certificate but it's underneath a certificate issued by my workplace, and the browser shows my workplace's certificate as "Untrusted". I don't know how certificates work, but I'm guessing this is the problem and what I need to do is somehow make my browsers trust my workplace's certificates.
Any suggestions for working around this problem?