Emby + TVHeadend or similar
Emby + TVHeadend or any one of a number of other USB tuner supporting services that are available as plugins for Emby. Emby server aggregates your stored media, and there are Emby clients for Roku, Android, LG, Samsung etc etc as well as a web client, or you can use Kodi plus the Emby Kodi plugin.
You can run it on Windows, MacOS, Linux natively (more or less) and they have Docker instances to get you up and running very quickly. I have setups using variations of this running on pretty low powered Intel NUC styles devices with a couple of TB storage for a number of family members. Anything with over 2GB or RAM and a 5th gen or later processor is more than beefy enough for direct play. It can also serve media to remote devices (including live TV) as long as transcoding isn't required (on low powered hosts).
Set up requires a little knowledge so isn't the quickest but, more importantly, use once set up is easy enough for a 5 year old, or an older relative with little to no instruction.
There's an Emby fork called JellyFin that happened recently due to a disagreement with the lead dev on Emby re open source but it's too early to see if it will have legs. At any rate Emby itself is mature and stable. Plex is an analogous service, however at the time I switched it did not support USB tuners, age restricted profiles and a number of other things it has subsequently caught up on, and Emby for me has more consistently responded to the community with improvements and fixes.