I have Jellyfin installed on a box which is located on the 2nd floor which uses WiFi, no choice unfortunately to run any cat cable anytime soon.

My router is on the ground floor with a 2.4/5ghz repeater on the first. My laptop and Jellyfin connect to the repeater on the 5ghz band and max out my isp plan on speed tests 300 up and 70 down. Jellyfin is set up to only work locally. Three TVs on each floor using the Jellyfin app on Roku or Chromecast.

The first and second floor are flawless connecting and no buffering. The ground floor is ok sometimes and other times buffers alot even when the network isnt busy.

How can i improve this? I could run a cat cable from the router to the downstairs TV Roku box. Or improve the WiFi adapter on the Jellyfin server it's just a AC1300 tplink to a AX2800 or something similar.

I'm not overly sure what the Roku box downstairs connects to, I assume not directly? Does the server send the media through the repeater to the TV or the router?

Any advice would be welcome, I know just connecting everything to cat6 is the real answer but for the next year what can I do in the meantime ?