I just have a plain TCL Android TV from a year ago and it's stuck on Android version 9 and I was wondering if there were custom roms I could flash onto it. I already de bloated it partially with the ADB command. I heard there was Lineage but you needed a raspberry pi or a box and not just a regular Android TV. Is there type available for just the TV because that would be sick if there is.
No there isnt because tvs use different hardwares, bootloaders, recoveries, etc. Each firmware, whether thats official or custom, needs to be tailored for specific device.