Welcome to the
Kitz forum . . . as a contributor.
As you have implied, the Huawei HG612 is now ageing gracefully and can be bettered.
I gather that you will be content to continue with a separate device acting as a modem and providing the local end-point for the Openreach tagged VLAN (101).
The unit of choice is, undoubtedly, one of the ZyXEL VMGnnnn-B10x devices. I shall mention two in particular --
I'm sure other member will be along shortly, to expand and enhance my initial list.