I'm not sure what you mean by this? There are LOADS of reliable Tivo models. I have some that have been working well over a decade. Yes, starting with the Bolt line there have been more issues than previous models. Probably most are drive issues since they started using 2.5" drives. I myself use a 3.5" CMR drive in external enclosure with my Bolt, has been working fine. But I'd say, overall, most Tivos over the years have been VERY reliable, at least hardware wise, some of the software/guide changes over the years maybe not so.
As for OP, I don't think the Edge has been out long enough to know how reliable it will be. It does use 2.5" drive and if the 2TB model drive is SMR. I really like my Roamios, for just recording (ie you say you don't care about apps), mine have been VERY reliable. And since they use 3.5" drives easy to upgrade or replace drives. One other thing, Bolt/Edge, when doing replacement or upgrading drives can lose recordings/settings when swapping drives around. Due to the Bolt/Edge having more info (the map to the recordings) on the motherboard flash memory. Guess my point is, if you are mainly using for recordings, maybe consider a Roamio. Since you will be getting an Edge you could sell it if you don't like it. Try a Roamio before going to Fios box, IMO.