Yesterday I came across this device Proscend 180-T. Basically a VDSL2 modem backwards compatible with ADSL/ADSL2+ in the form of an SFP. Though I think it is actually I think this is just a rebadged Metonia device. They also appear to have a G.Fast version in the works.
The best I can find is that you can configure/talk to the SFP using special ethernet packets, though there is very scant information on that.
The following are some places that seem to actually be selling it, the first is another rebadging in the USA, the second in Greece and the third in Australia.
https://www.versatek.com/product/vx-160ce-vdsl2-sfp-modem-remote-telco-grade/
https://www.nsys.gr/en/proscend-180-t-vdsl2-sfp-modem-module-telco.html
https://www.nsys.gr/en/proscend-180-t-vdsl2-sfp-modem-module-telco.html
They would make a really cool addition to the new ER4/6 lineup. Any chance Ubuquiti could offer badged versions with an update to EdgeOS to enable easy configuration of the device?