DIY wirelessly extending network

Hi folks

Got myself in an annoying home networking position and keen to hear some advice.

I have a setup with 2 computers which require decent bandwidth. A desktop which is used for gaming and streaming among other things, and a linux server which hosts a bittorrent client, filesharing, plex server, etc. Both of these sit on a desk, previously ethernet'd straight into a router which ethernet'd into my fibre box (ONT). Neither have a wifi card or any way to connect wirelessly. End result was both got 100mpbs down/10mpbs up which is what I was paying for. This setup worked well for me.

Fast forward to now, I've just moved house and the ONT is on the other side of the house. I've signed up to a 200 down/20 up plan which works great over 5GHz wifi in the same room or ethernet plugged into the router.

I need a way to get that sweet 200/20 over to my desk. First I bought and tried an ethernet-over-power kit (which I've had success with in the past) but they didn't connect - different circuit breakers, I guess.

Then I tried setting the router on my desk (which was previously just being used as a switch) to WDS mode, so it intercepts my wifi signal from the router plugged into the ONT and outputs that via ethernet to both desktop and server. The thing is, my desk is far enough away from the ONT that the wifi in this room is poor (tested both on my phone + desktop using the WDS). I'm getting anywhere from 4-40mpbs which is painfully slow and worse - inconsistent.

So the question - how can I improve signal strength to my desk, preferably up to the 200/20 which I pay for? I can spend some money if I need to but prefer some DIY hack if possible. Slightly salty about shelling out the $100 on the EoP kit for it to just not work.

Any suggestions or tips welcome, especially if it's worked for you in the past. Happy to provide specifics on model numbers etc if it's helpful.

Thanks for your time & appreciate your help in advanceara