>>/1673/
I've excluded the Hydrus Network directory from Windows Defender, to no effect. The cacert.pem file is in place, haven't checked what's actually being read yet but it seems normal.

I don't have any special environment that's relevant to this as far as I know, but I am a software engineer so there could feasibly be something. Only reason I'm not 100% sure there's an environment issue is because it worked fine with the old version, even though it was years old, and the rest of the application worked fine after update. So presumably in that time there was some dependency change that now interacts with my environment, that was isolated in the past.

It can fetch HTTPS URLs, such as https://endchan.net/hydrus/res/1669.html , fine via debug->network actions->fetch a url, and it can download and import files fine via downloaders, from https urls such as https://danbooru.donmai.us/posts/3579168 

Only PTR seems to be the problem. I've tried removing the PTR service entirely and re-adding it via the standard help menu, too, which had no impact (other than leaving me semi-tagless).