Good to hear you've gotten their modem into bridge mode, should make things much easier. Glad my provider that uses VDSL2 requires the setup to be in bridge mode. They tend to provide very specific router advice too, for the ones known to be able to handle the speed their connection can offer. Though most of their customers are now on direct ethernet connections bridged over to the fibre network instead of VDSL2 being the bridge to the fibre.

Only downside, the VDSL2 modems they tend to use have some IPv6 bugs likely to not be fixed. It's why the IPv6 rollout attempt here was rocky, was difficult to test from home. Not sure if I'm going to seek to replace the modem, or just live with it till I leave this current place.