Just an update;
Right after installing GOS, I installed RethinkDNS and had it running. After that point, I encountered many connection issues (e.g. slow speeds, connection interruptions, failed GOS updates and downloads even though the system was given full access via the firewall and DNS filter).
Yesterday, I disabled and uninstalled RethinkDNS and all of these problems disappeared. While I don't have any explicit proof, I believe that Rethink's using the VPN service while not actually being a VPN service (at least not yet) is causing issues. See [https://grapheneos.org/faq#ad-blocking-apps](https://) YMMV.