I would set up a "MoCA" system to extend your network. MoCA in this context stands for Multimedia over Cable Alliance".
MoCA does use your cable coax vs lan ethernet cables to go room to room,
so you would need to have coax cable connectivity in each room you want to connect, typically.
Plenty of YouTube videos on this method of getting internet from a far flung router to a distant room or rooms.
Here's one link explaining it:
https://youtu.be/dm_Znyh7uZ0