smb://user@ip-address works while smb://user@host does not

You’re correct: it combines modem and router and wifi.

I did end up assigning static addresses — which was really easy with the new modem/router. The thing is, I only need them static to make the /etc/hosts file trick work.

Weirder still is, that the modem/router does say it has a DHCPv4 server and a DHCPv6 server. I can only toggle the DHCPv4 server from enabled to disabled, while the DHCPv6 server can only be toggled from stateless to stateful.

I thought so as well, but without the /etc/hosts file trick, pinging the host still gives “ping: unknown host”.