I have never said it is impossible or infeasible to use a third party router with DV. However, it is impossible without the use of a SH2.
It is a simple matter to put a third party router behind the SH2, but the SH2 is always required.
Even with option 2, the SH2 is still required, but instead of being the primary router, it is just hung off a LAN port of the third party router.
I went through hell with BT to get line installed and had to get CEO complaint as engineer called and said sorry can't install fftp as you don't don't have box fitted on pole. It took from Sept 5 to Nov to get install done. Then they still Ffed it up as no incoming phone line. So not sure they would be overly happy for me to ask for another phone line, as hub does have a dect output
I've had days with no problems, yet Sat night they must have been working on the line somewhere from 6-11pm as that is when skyQ box had reboot glitches
I have since found out that ipv6 can cause issue on your own router. I may have had mine on wrong option, so as a trial to see if it made any difference to glitches I set it to bridge mode as this lets more traffic through