I use the default rules for Firefox as a “web browser” (at least I think they were default), with “ask and log” in the end. Ever since Firefox was updated to 90+, Comodo firewall has been asking me to allow various UDP connections (mostly Google’s and Cloudflare’s IPs). What is that all about? It wasn’t the case before, but I remember Vivaldi was asking for such connections. Nothing changes in either case, whether I allow them or not, though.
Maybe it’s related to the new http3 / QUIC protocol.
More interesting info can be found here: HTTP/3, the new HTTP protocol based on UDP | Stackscale
Interesting, thank you both for the answers, I wasn’t aware of that. (In Vivaldi it has something to do with streaming/multimedia, I believe.)
I don’t use DNS over https yet, though (that setting is unchecked). I have to check whether OpenDNS supports it this way.
EDIT: Turns out OpenDNS supports it via doh.opendns.com. A more generic related question: If I set this to on, is the etc/hosts file observed by the browser (so, checking hosts first, DoH later)? I have some blacklist there.
The local hosts file has priority over a (Open)DNS lookup.
On the OS level. But the application can ignore this, I suppose? (As for Firefox, it seems to follow the rule, though.)
The majority of all applications do follow the OS level.
Sure, there are ways to bypass using hosts file. Google and you’ll find some ways. Some of those ways are not very common though and I’m not sure if an application could use one of these bypass methods without requiring any user input.