Since most of the 1000Base-T1 gear is still unreasonably expensive/effectively impossible to get quickly in small quantities, you can run 100mbps and 1gbps Ethernet over "reasonable" lengths of single twisted pair using MoCA adapters plus coax->twisted pair baluns. Achievable cable length will obviously depend on EMI conditions, but I've had reasonable success with this method on twisted pairs in industrial robots.
GIGA G4201TM modems are built for exactly this, using the G.hn standard, over a single pair. I’ve been using these to avoid digging into walls to replace wiring — they claim to sync at up to 1700mbps and, even in the real world, I’m saturating the 1000BASE-T ports.
