So I’m pretty new to self hosting as well, but I use Tailscale. They also have the option of working with Mullvad, though I’m not 100% on how that works. Tailscale is a VPN itself, and it’s allowed me to access all of my self hosted stuff everywhere, including on my phone. It’s been really nice, though I understand people might not want to use corporate methods.

Gluetun to my knowledge, when I use it, is just for my qbittorrent stack to access my VPN.

If you don’t want to use something like Tailscale (there’s also a self hosted option called Headscale, and others like Zerotier and I think Netbird?) there’s opening ports and using reverse proxies. I would be really careful about that one, but hopefully I’ve given you some options to look into.