My house is probably 25 years old. It was wired with CAT5 but it was only used for old fashioned POTS two wire telephone. All the jacks around the house (9 of them) are RJ11 telephone plugs. The wires all meet up in the garage at a patch panel near where the old phone service and DSL came in.
This week I removed the old patch panel, pulled all the wires up into the attic and put ethernet connectors on them. Then I went around to all the jacks in the house and replaced them with ethernet connections. Making those plugs was tricky and took lots of re-work (I estimate a third to half of the ones I did were bad). Pushed them through the wall in the attic into my office and made this slick little recessed patch panel. Gonna buy a 16 port switch and put wired ethernet thought the house. There is even a connection outside on the back patio. That stray coax cable is for my Spectrum cable modem.