At the end of 7.16.20 installation, my AVG antivirus said that "boinc.scr" is infected by IPD.Generic.
I created exception for this, but it's not a good message to see.

It's a very common observation after the release of a new computer program. Modern anti-virus programs do far more than scan the files stored on your hard disk for known threats. They commonly also include behavioral analysis, which the boinc client (in particular) can trigger: the boinc client doesn't have a visible screen display, uses your computer at high power, and communicates extensively over the internet. All very suspicious!

The other thing that AV programs can do is check their company's database of known programs and their reputation. New programs don't yet have a reputation, and haven't been though a full evaluation in the AV company's labs. So they can panic: the fuss usually dies down in a few days.

It's slightly unusual to see such a report on the screensaver module within boinc: that will have changed little, if at all, in the new release, and it doesn't exhibit the same suspicious behaviour as the client. But the general advice with an unexpected warning like this is to check the offending file(s) with a service like virustotal, which can compare the reports on an uploaded file from a range of independent anti-virus products.

This has reminded me to install clamav on my Linux box. Haven't done any checks since I got the Ryzen machine. In fact the old logs from my home directory that was copied across don't show a scan since 2017 when a couple of emails with dodgy attachments came in. (My reason for installing it then) The suspicious files were indeed dodgy but only capable of infecting Windows computers and given the suspicious nature of them were unlikely to be forwarded by me to anyone else.

And nothing in my WINE installation of 7.16.20 showing up, though a number of other things did, mostly in my firefox cache that are harmless to Windows never mind a Linux distro.

The other thing that AV programs can do is check their company's database of known programs and their reputation. New programs don't yet have a reputation, and haven't been though a full evaluation in the AV company's labs. So they can panic: the fuss usually dies down in a few days.

I know it's a false positive, but it's annoying for a first-time user

There's exactly nothing we can do about it, as it's AVG that throws the warning. So if you have to ask someone to fix it, it's them.