use an old laptop with hdmi output
or a pi or an android tv box

you can use steam link app on it to stream from a gaming pc over lan/wifi with no problems
just use a wireless k/m or controller for games or desktop control

you could configure it so that your pc outputs the same signal to both the monitor and the tv.

The long (and reliable) hdmi will likely be the most difficult part tbh, they get expensive, fast, expect £70 to £200 for a fibre optic one, I've had most success with a brand named ruipro, I went through a LOT of 5m hdmi cables and they are the only ones not to degrade within a month.

As for how to control everything, id suggest to just mirror the TV to the desk top screen for ease of use and if you don't wan tor run upstairs to turn it on you can buy a remote Google / check amazon for ' SilverStone SST-ES02-USB - 2.4G Wireless Remote'Ive used one for a whole and it's great.

For your keyboard and mouse or a game pad the cheapest way is to uee usb over ethernet adapters from your pc into a powered hub by the TV, I am using ' LogiLink UA0021D - USB 2.0 extender ' (again Google / amazon) with a 15m ethernet cable to hook up my stuff and seems more reliable and far cheaper than very long usb cables, the plug them into a powered hub of your choice, I've used a sabrant one for several years without issues.

You could also just use a mini pc and stream from your main one via a ethernet or wireless network.

Old computer is your best bet.
You can remoteplay from your main computer.

I have an old mini pc 3rd gen i5 with windows 10, which i use to play Detroit become human, cyberpunk 2077, and other games, using remote play, it automatically opens steam in big picture, so no keyboard needed.

edit: obviously my old mini pc wifi is bad, so i had to put lan cable there.
But there's a lot of 9th gen pcs around pretty cheap with way better wifi chips.

how far are these two apart?
there are 2 ways to go about this.

the best would be to have a local "nas/mini pc" device near your pc (does not have to be powerfull)
have it set up to share imput and monttor with the pc (shared control) and connect the two with a fysical etherner cable...
-> than you can just connect your tv by short hdmi cable to this device and have wired or wireless control communicating to this device at short range.
**an ethernetcable can be plenty long to reach anywhere in your house


IF the range is short enough you might be able to do this :
you need to draw an HDMI cable directly from your pc to your tv (max lenght 10 meters or something like it)
you need to draw an USB extention cable directly from your pc using usb extenders and hubsan usb hub.. (3-5 meter per cable, with an signal booster between them and a hub at the end max 30 meter total)

option 3 share screen.. via wifi.
this will add lag, but there excist apps that allow you to vieuw whats on your pc screen on any other device in your own house (like I can watch (and control) my pc from my phone, tablet, and laptot and so on)
**various ways to set this up but basicly you use remote desktop and have the tv as your display, and your controller or keyboard-mouse near your tv as the control.

final solution :
bluetooth might be able to allow you to take a wireless keyboard and mouse far away from your pc to control it directly..
-> than you just can set up wireless hdmi to connect your tv..

ofcourse the shorter and more direct (and fysical) the less the lag.

personally I would just set up an old pc or buy a cheap nas (it can be a really low end pc).. near your tv... draw a fysical ethernetcable between it and your pc.. and set it up.

that likely gives the best quality of connection.

The network card dictates the cpu selection. So you get full use. Then software selection. Last. Full it with drives.

I use win server 2022. Remote desktop. All ports are empty physically. Not even keyboard/mouse.

It does dns, dhcp, printer, wins, and smb's

Thanks for the great answers.

For going the LAN on crappy PC next to TV option, my gaming PC is connected using ethernet cable for internet and it only has a single ethernet port, so I would need some USB to ethernet cable, then I'd run that cable all the way to the TV PC and just connect the two physically (ie no in between router)?

I looked around a bit and it sound like at some point remote play would default to wifi (which I would probably need to use on the TV PC) even if direct connection was available but that might have been fixed?

Sound like ether way I go, I need to run a ethernet cable (like cat 7 or something) between the two, which would be about 10 meter or so, hoepfully the connection doesn't suffer from that distance.

I'll keep weighting my options, thanks.

You just need a basic cheap switch, Internet to it, cables out to where you need them, tada they are all networked, plus a step or two, but both pc's will be able to stream from one another.

I have a power strip and USB hub with long cable halfway between the TV stand and the easy chair for mouse and keyboard dongles and charging. And a swiveling tray for the mouse and keyboard, though keeping the keyboard on the lap, and the mousepad on the arm rest is also stable enough for some gaming.

Wholenits not the cheapest approach you can get lap boards or something like corsair lapdogx which is a wireless k63 mechanical keyboard with a frame it bolts into that also has a mouse pad on it, could be worth looking into.

Get yourself a Steam Link box or you can use the software version of (Steam link) for Windows. https://psteamcommunity.yuanyoumao.com/app/353380/discussions/8/597410919908370593/

I have my computer setup on one side of the living room. I got a 10m HDMI cable that I will run on the wall to hook up to the TV. Wireless keyboard and mouse (and some tray or whatever) and an XBOX controller.
Don't have everything setup yet but I tested it and it works just fine. The TV is also were I play with the XBOX, so, the same setup on the couch.

Depending on the distances, you can use HDMI over ethernet cable with some adapters.

there are steam link apps for pretty much anything
android tv, apple tv, apple ios, mac os, windows, linux, pi

you can use pretty much any bt controller if the client has a bt dongle
or a wireless k/m using its dongle to the client, dongle or bt