I've built a 2nd/3rd generation Intel PC out from a Small Formfactor HP machine.
Put 8GB of memory into it and a 500GB HDD. The whole thing costed me around... 35-40USD and got a remote for that machine for 20USD. It's under my TV, in sleep mode so the remote can wake it up any time and the Power button on it puts back to sleep.
Running libreELEC, which is a Linux system built around Kodi, and for Kodi there are lot of streaming plugins available - Netflix too. It can pretty much play back 1080p without issue, and maybe even 4k, but I couldn't test it properly because I have a Panasonic plasma TV and that's only full hd.
Had some stuttering issue with Wayland, but with x11 it runs perfectly. If I set up the video player to synch framerates at the beginning and end of the video, it runs smoothly.
These plugins use Kodi's UI, so they are easy to navigate. It can't get more comfortable than that, Kodi is way better than any shitty Smart TV system out there, especially those Android TV abominations.
So yeah, a 2011ish PC, a DVD/Blu-Ray drive, USB remote, libreELEC and you never need any other media player equipment.
One thing needs to be done, tho... I have to use DisplayPort <-> HDMI for video out and the adapter doesn't really communicate with the TV so have to build an USB/LPT-CEC interface for it (Arduino or Pi Pico) and with that, the TV would turn on/off, change to AV or back to TV when the power state changes of the PC and also would be able to control Kodi with the TV remote too.
I now have a simple USB remote control. Since it's USB, it can wake up the PC from sleep when I press a button on it.
The USB-CEC would basically emulate a keyboard and send keys for the PC accordingly the CEC message the TV sends. If the PC is in sleep, the USB adapter could wake it up.