

If by RJ45 you mean erhernet over standard 8P8C (i.e. RJ45) your looking for SFP-T modules. Can’t connect that to your DSL line though since that’s not Ethernet.
There do seem to exist G.fast sfp modules for dsl, but do note that sadly sfp module and router brand incompatibility is sadly a thing.
Related note: At our company we also had quite some issues getting some of these more special sfp modules working (e.g. XGS-PON), so ymmv with a dsl one.
(If you’re looking for a device to plug sfp modules into, I can second MikroTik here. They’re also great about accepting 3rd party SFPs)

Which fiber provider doesn’t support IPv6? I thought it was only Swisscom mobile and its subsidiary’s which don’t support it (though from what I heard, even that is in testing now)