Hey fellow self-hosting lemmoids

Disclaimer: not at all a network specialist

I’m currently setting up a new home server in a network where I’m given GUA IPv6 addresses in a 64 bit subnet (which means, if I understand correctly, that I can set up many devices in my network that are accessible via a fixed IP to the oustide world). Everything works so far, my services are reachable.

Now my problem is, that I need to use the router provided by my ISP, and it’s - big surprise here - crap. The biggest concern for me is that I don’t have fine-grained control over firewall rules. I can only open ports in groups (e.g. “Web”, “All other ports”) and I can only do this network-wide and not for specific IPs.

I’m thinking about getting a second router with a better IPv6 firewall and only use the ISP router as a “modem”. Now I’m not sure how things would play out regarding my GUA addresses. Could a potential second router also assign addresses to devices in that globally routable space directly? Or would I need some sort of NAT? I’ve seen some modern routers with the capability of “pass-through” IPv6 address allocation, but I’m unsure if the firewall of the router would still work in such a configuration.

In IPv4 I used to have a similar setup, where router 1 would just forward all packets for some ports to router 2, which then would decide which device should receive them.

Has any of you experience with a similar setup? And if so, could you even recommend a router?

Many thanks!