I see, that makes a lot more sense then. Always fun when "upgrades" remove functionality.

Residential ISP routers are almost universally trash because most people just want to receive media streams on at most a few devices at a time.

You might be able to set static routes in the ISP router so you can run your own router with its own subnet and have all your addresses routable within your home network anyway. If you have your network on 10.0.0.0/8 and your router is 192.168.0.2 on your ISP's network in your house, then you tell the ISP's router that 10.0.0.0/8 is reachable via 192.168.0.2 and cross your fingers that it can route IP correctly. Unless the ISP's router advertises that static route via DHCP, other devices on the ISP's network in your house will likely need to be told about your network's routing in order to be able to communicate with devices on your network. MDNS name resolution is unlikely to work across the two networks. Some other features, such as automatic port forwarding, may not work, but may be possible if you tell the ISP router to forward all ports to your router by default.

In my network I run DNS so everything is resolvable by name. Most of the time the names are filled in my autoconfiguration. Some K8S services are connected to the rest of the house by Multus so they have their own IP addresses.