I'm in a similar boat, switched from Android TV clients to a couple little beelink N100 boxes (which are great). I use Kodi as my Jellyfin client which works great especially with a remote/from the couch, and a cursory search would imply that Kodi has plugins for Prime Video and Disney Plus, but I don't use those, so I have no first-hand experience.

The big one that annoys me right now is the lack of a TV interface for Spotify outside of the walled gardens of Android, Apple, and Roku. The desktop app does not play well with anything but mouse and keyboard.

Another thing to note is that Jellyfin Media Player plays really nicely on a TV/Remote control setup.

AppleTV

Roku

Firestick

Édit: Downvoted for a legitimate answer? This is why people don’t want to post/help when people ask questions.

I am reasonably pleased with my TV UI approximation. It’s an old Skylake-era CPU running Windows 10 Enterprise IoT LTSC which lasts until 2032.

I chose windows because Linux is often limited to 720p browser streaming. And I got tired of overcoming hurdles to make the thing work well, forget what they were but damn they sucked and took a lot of time. Burned through a ton of my self-allotted time fixing stuff till I just ripcorded Win 10 Ent IoT LTSC; Linux might go better for you!

Anyway, it’s at 150% desktop scale and I have the task bar auto hide. I have icons for all streaming sites, Freetube, and Jellyfin on the desktop arranged in a grid. It looks reasonably good, they open in Firefox or in their apps. I close the whole window when I’m done (I don’t use the browser’s tabs), which helps with the “TV box” feel of usage.

I have a remote that has some IR functions to turn the TV on and off and change inputs along with gyro mouse control. It’s hella China, just buy one on your relevant China source (Amazon, alibaba, etc.) - there are tons of clones. The light up feature on it makes an audible hum, so that sucks, but I don’t use it and don’t seem to miss it.

Best bonus is it blocks ads on all the streaming services I have (uBlock origin mostly, also AdGuard but I think uBlock Origin does the heavy lifting). And can turn on WireGuard for modern account sharing, going to automate it soon for certain streaming services.

I use a browser on a desktop OS (Linux). I get what you mean that a browser on the tv is not nice UX, but there are some things you can do to improve the experience such as

• bumping up the default zoom level (I prefer to do that at the OS level rather than in the browser settings so it also makes menus, buttons and other UI elements bigger)

• getting one of those small wireless keyboards with integrated touchpad. The one I use is from Logitech and the batteries last for months.

Not everything is in the browser, I have downloaded a few desktop apps from Flathub (Freetube for watching Youtube, unofficial Spotify client etc).

The level of freedom you get from a desktop OS is so great that I would never go back to a “tv box” like Apple TV and similar things (I tried those and concluded they weren’t for me).