>And if you rent rather than own, you likely can’t add cabling at all under the terms of your lease.
A POTS phonejack can use pair(s) in CAT 5 (or 5e, 6), and newish buildings often already run it to the wall jacks rather than CAT 3. Depending on access to the other end of the lines, and appetite for DIY upgrading a landlord's building, it's quite possible to temporarily swap the RJ11 hardware for some RJ45 and have a wired LAN ;)
A POTS phonejack can use pair(s) in CAT 5 (or 5e, 6), and newish buildings often already run it to the wall jacks rather than CAT 3. Depending on access to the other end of the lines, and appetite for DIY upgrading a landlord's building, it's quite possible to temporarily swap the RJ11 hardware for some RJ45 and have a wired LAN ;)