Uber...do you still have your Bluesound equipment?  I’m guessing not or you would have tried it by now.
  I upgraded to the Bryston BDA3 for my main system but there is no Amazon tab as of yet.  I still have my Bluesound equipment (mainly using the Node2 into two HT systems elsewhere in the home) but I am gun shy about doing a BluOS update, and have avoided doing them for months, because doing updates had led to problems in the past).  Maybe I will just wait for Bryston to add Amazon 
but I am gun shy about doing a BluOS update, and have avoided doing them for months, because doing updates had led to problems in the past).

I've had my Bluesound Node 2 for quite awhile now.  I have done every update, (probably around 6-8 total).  Never had an issue.  None, nada.  Went perfect every time.  Not sure what problem(s) you encountered, but I sure haven't had any...
Mahler.
I remember you seemed to have had a lot of issues on your Bluos updates whereas I am in MoFi camp where I never suffered at all during updates.

However yes the Vault is long gone.
I have had ZERO Update issues with the two BLUOS Node 2i that are used in two separate systems.

Cheers......
My hope is that Roon partners with Amazon's Hi-Res group and offers it, if they do, I'll try it out...and probably terminate my Qobuz and Tidal subscriptions.