waydroid is pretty easy to get working - and I think will be usable by the actual end user once set up.
I did look at stremio but I couldn't see a way to do the offline downloads thing on netflix.
That is a desirable feature for the person who travels a lot and they just want to have some videos for when they're off-line or on limited bandwidth like on the train or bus.
This servarr thing looks way more complex - though I admit I might be a bit too dim for it as I couldn't figure out what it actually does.
Thanks for the suggestions though - waydroid looks easiest to meet all the needs. I'm sure someone smarter than me will have fun with that weird servarr suggetion - it does seem to have a whole lot of features.