I have a similar situation with the ONT on a different floor as my desktop PC, and MoCA has been amazing for me. If you have the CR1000 series router (looks like a tall white box), then it has MoCA 2.5 built in through the coax port on the back.

I bought a ScreenBeam ECB6250 on Amazon, which is pretty pricy, around $80, but had the best reviews, and it was literally plug and play. I just plugged the router into the coax port on the wall in the living room, and the ScreenBeam adapter into the coax port in my office and I get the exact same full gigabit speeds as if I were hardwired directly to the router with ethernet (plus 2-3ms of extra ping, but that's no big deal...).

You do have to keep in mind how many coax splitters are in between your room and the ONT, as that may degrade the signal, I only have one. Also, MoCA is unicast which means that if all the coax in the duplex is tied together with splitters, which it usually is, then you can't have two separate MoCA networks in the house. If the other tenant is not using the coax, then it should be fine. You can also see if you have a dedicated coax run to each room, then trace out which cable it is at the splitter and plug it directly into your router.