Thanks to the answer, the bit about self-hosted servers connecting to Raven's master server was enlightening. Apologies for the late reply, I was hoping to get things working and only then reply, and guess what, I'm still stuck.
I can't port forward because of CGNAT, I've known this since I tried a Minecraft server last year. Now me and my friend tried Hamachi using this guide. I managed to launch a server and join it, but he couldn't find it in the Local server list. We found out we couldn't ping each other, fixed that after changing firewall settings and he still can't find it. He'll try port forwarding on his own, but will take some time to get it done - we still don't know if he, too, has CGNAT. It should be straightforward if he doesn't, but otherwise the Hamachi workaround has so far reached a dead end.
If it helps: I'm using this as my server.cfg, server.bat and serverjoin.bat:
The sv_master1 line is probably useless in a pseudo-LAN server. For the serverjoin, we've tried with both of us connecting to my address, and each one having a different file, and it didn't make a difference.