How can I improve my home internet connection in an old house?

You're not alone in this. First, check if your place has any other wiring like for landline phones or cable TV. If you can set up an additional access point with a wired connection using an adapter, that could provide a really stable network.

Using Ethernet is definitely the way to go for speed and low latency. If you have existing coaxial cables, consider using MoCA adapters; they can work wonders. Otherwise, powerline adapters can be an option, but they're not the best if your electric circuits are different. If you can, try to avoid powerline adapters unless it's your last resort.

If running a direct Ethernet cable is possible, that's really the best method. Ethernet can reach up to 100 meters, so it doesn't have to be perfectly straight—feel free to route it wherever necessary, even outdoors if you can swing it. If that's too tricky, try using powerline network extenders or MoCA adapters if your house is set up for cable TV. If all else fails, a mesh WiFi system might help, but there could be some latency issues to consider.