General DSL Support

What are the main challenges in supporting a DSL modem? I believe I have heard before that most DSL drivers are closed source, is that the main barrier? Do we need a manufacturer to release a driver to the community (similar to the genesis of the mt76 project) before we can really see widespread support for DSL modems?

FOSS drivers.

https://openwrt.org/docs/techref/hardware/xdsl

hello,
you can use a technicolor Modem/router Like
DGA4130
DGA4132
TG800
TG789vac v2
They are all runing on Openwrt Chaos Calomer 15.0.1 and can be rooted with several exploits.
see here : https://www.crc.id.au/hacking-the-technicolor-tg799vac-and-unlocking-features/
or here : https://forum.kitz.co.uk/index.php?topic=20343.0
Once rooted you can do everything you want with hardware NAT and an optimized DSL driver (Broadcom)