I'm running 23.1.6 but was having similar issues before
I've noticed if I try to access https://en.avm.de which is for the fritzbox routers the webpage times out, I'm also getting similar on other sites as well.
I've checked and even disabled zenarmour and that is not blocking the sites, checked firewall and that doesn't seem to be blocking either. No geoip settings enabled
If I switch device to use mobile internet it works fine, other than fully remove opnsense or rebuild it I'm not sure where the issue is.
Any ideas?
OPN by default won't stop a client going to a site. It has to be a setting you have somewhere on of off OPN like for instance a dns blocker on OPN or a separate device like a raspberry running pi-hole.
You could try developer tools in a browser if the client is a pc and/or do packet captures.
Did you figure this out? Because I've been having the same issue with the latest release. Mostly https web sites, but an unusual set of web sites.
I'm wondering what you did to solve it.
Even if there are no special things like zenarmor or blocklists in place, there can be at least two other reasons why some sites fail:
1. Bad IPv6 setup
2. MTU too large, especially with PPPoE and/or VLANs