You would have to break your back to find an am21 anyway. The database setup was doomed to fail, let the thing scan, dish rarely has problems with that. Anyway, it says 7 simultaneous recordings and 7 active rvu sessions, a recording isn't an rvu session so if you are recording 7 things could you watch 4 other things live? I'm sure the extra tuners are for 4K (as the 54 has 7 but only uses 5) but why couldn't you utilize them if you're not watching 4K?
As for the am21 Direct obviously doesn't want subs to use them as they have never really been supported by them, they should still have the ability to use them in the new system ...
Directv made a mistake when they removed the tuners from the recvrs .... people complained that they couldn't get thier OTA channels, D* thought that at the time the limited number of Locals they had available was gonna do it for them. D* expects you to just accept that they have Locals on the sat for you, but they don't give you all of the ones people want ... I don't need a bunch, give me the main Big 4 and maybe MeTV and I'm good, others aern't.
Anyways, after D* got enough complaints about the Locals, the AM21 appeared, this worked well as it integrated the locals into the D* guide.
Now you could record your OTA channels again.
Now the AM 21 is being phased out, if not gone already.
Where do we go from here, if you can't get locals from D*, you can't record them ... thats a huge step backwards.
Example, I just got back from Texas where I had no locals available to me from D* because they are on the 119 Sat and I could only get the 101 with our current set up.
No longer taking the Slimline dish down there. Automatic Dome works great, except it only gets the 101.
Therefore I needed to use an OTA antenna, which I did.
According to D* in the future, I will not be able to watch the locals when I travel ...