I’m going to be using an SBC for this, which doesn’t have the capacity for an extra storage drive. Also, I’m planning to move in a couple of months, and I wouldn’t want to deal with storage in the middle of all of this. The cloud isn’t as insanely expensive as I initially thought; B2 is $6/TB, and I hope that with reencoded streams at an OK resolution I wouldn’t go beyond 1.5TB a month (I’ll be deleting stuff with bucket policies, of course).
I’ll take a look at tdarr alongside ffmpeg, thanks!