The simplest, lowest power way of playing content is, as others have said, to use a USB hard drive and plug
it into a TV with a USB port - assuming you have a USB port on your TV (my TV has one, and it is not a smart TV). However note that the TV may not have the necessary codecs to play all of your library: over-the-air (OTA) broadcasts and DVDs use MPEG-2 coding but everywhere else you will typically find other, more compressed, formats (e.g. H.264, H.265) that your TV will probably not be able to decode. You could translate these formats into MPEG-2 but then you would be taking up more disk space plus waste a lot of time.
If you want an off-the-shelf system you could buy an inexpensive media server system, typically running Android. They are very flexible and will likely solve the problem although glitches are not unheard of. If you have some computer skills then put together a media server with a Raspberry Pi; media server images
are available for install on a micro-SDcard to plug
into the Pi and you are off and running. Go with the Pi 4 as you would notice the performance difference. My personal solution is to add media software
to my small NAS (network attached storage
server) which I use primarily for backup storage
. I also have an HDhomerun for receiving OTA TV; this receives and passes broadcast TV to the NAS for storage so I can record
shows for later viewing. However my server does not have an HDMI port so I still have to run playback through another device, such as my laptop
or a casting device. Recording is a huge win, not just for the otherwise missed shows but for being able to skip commercials and play back at a higher rate. (News shows can usually be viewed at 1.5x speed, and some like Amanpour at 2x.) BTW you can speed up YouTube playback in the settings.
My ideal would be to have a NAS with HDMI output. My Synology NAS is losing support soon so I may have the opportunity to change. QNAP offers systems with HDMI.