Not a Chrome user, but didn't they recently bypass the system DNS in favor for their own? If so, a slow DNS could explain it as well.

Yeah but that's experimental and it's supposed to have failsafes and fallbacks. I guess it's possible that it malfunctioned, and I'd never rule out DNS more generally though.

I meant the other way around: Google's DNS being fast and the local one being slow. At least I've experienced on more than one occasion my ISP DNS taking forever to resolve some domain where Cloudflare's or Google's DNS responded quickly.

Oh I misunderstood because Firefox also started experimenting with DOH lately. So it could be either, yeah!