You also (and many people could not wrap their heads around this) didnt give up privacy for your emails - Helm provided you an IP and proxy (via ec2) but assuming TLS protected SMTP connections (most are these days), inbound mail was protected with a cert that lived on your device, and outbound protected by the cert of the server you were sending to.
The home server was configured using a smartphone app but they kept choices to a minimum and made the setup process quite painless - adding my Helm to my iPhone was one click and one authorization IIRC and on my Mac similar (my linux laptop was only slightly more complicated).
You could put N domains and N users on the box - there were probably some upper limits there but I ever hit them. I had multiple domains and accounts though and it worked smoothly.
On the consumer side, I always found the biggest issue was trying to explain to people how it all worked. The people who cared about privacy tended to be skeptical that a pre-boxed home server with an ec2 proxy could be truly private, while everyone else didn't want to give up the convenience of gmail and webmail (oh ya, it offered no webmail - not a problem for me but I think some people definitely went to Protonmail instead because they prefer webmail, even though Protonmail unlike Helm can see all your email that is not Proton<>Proton or GPG encrypted).
But reading this, it seems pretty clear demand was way less of an issue than the supply side - Giri here has multiple stories of getting screwed over by contract manufacturers. Oy. It was a heroic effort at privacy tech and I was pretty bummed to see it fail.
Giri if you're reading this, thank you and your team for trying so hard. I loved the product and the spirit (rare in the Valley) of embracing privacy in a constructive, positive, non defeatist way. This was an extraordinary product on many levels.