He already has an android box on which he can use kodi or libreelec for video / photo/ music viewing purpose,. myth tv can connect to android box easily since its a dlna server i think. he doesn't even need myth tv since he can connect the android box directly to a shared drive or use a portable drive and watch media off it.
The more i think about the recording tv series option, the more dumb it seems. I mean there is hotstar, sony liv and other apps available on play store to view old tv series for a yearly fee. the yearly fees are around 499-1.5k i think. he can install apps on his android box and stream the tv shows if he has a good connection. not many advertisements in them too compared to the 15 minutes advertisements you get when watching live tv.
Reading the first post again, I'm not sure if op has a local cable box or an stb. He hasn't mentioned anywhere he wants a media server, so i suggested an extra unit.