I recommend a Roku streaming stick or a Roku streambar if you need a decent sound bar too. That's what we use on our "smart" TVs and I hate ads too. Full disclosure: they do put one ad on the homescreen off to the side, but none in the actual content apps. You'll only see it while between apps.

I stopped using Plex a few years ago. Now I just cast the video to a Chromecast. VLC or cast via browser.
It's not going to work for remote, but if all you want to do is cast movies to a TV, it's a simple solution

Also as a bonus, you can cast a lot a streaming media without commercials by using an adblocker.

Do you have a games console? Xbox & PlayStation have Plex apps and are able to handle lots of file formats nativity. HDMI CEC is pretty neat too, you can use your tv remote to control media and navigate Plex on the console.