I think you've rather missed why Ubiquiti products need so many firmware updates.... They launch them BEFORE they're actually ready then they issue a swathe of updates to add all the features they should have had when they first launched. UBNT also have a fairly good track record of launching half-baked products then abandoning them when they don't sell especially well. Amplifi would seem to fit that bill very nicely. You only have to spot that Amplifi is the only UBNT product that doesn't have it's own sub-Forum on the UBNT community pages to realise it's another unloved skunk-works project that they launched because they thought they ought to have something like that in the range.
ALL the other UBNT WiFi kit ditched 802.11 k/v/r over 18 months ago because they came up with a proper system that actually works.
None of these mesh systems are especially great, but if you want a UBNT mesh product, buy one that is actually supported and that means you want the Unifi Mesh-AP or Unifi Mesh AP-Pro. They're proper, fast, wireless access points that work properly with just a power connection.