I agree wth eveything you wrote… The only thing I would add is that the wall wart that comes with the Rivo+ is 5 volt, 3 amp. So, that is why I would suggest 3.5 amp and above. The Lineo5 rating of 5 volt, 5 amp is more desirable, but, for those of us that are not permitted to buy the Lineo5, this 5 amp rating is harder to find and more expensive. I am hoping since the standard wall wart for the Rivo+ is 5 volt, 3 amp, that the higher rating of 5 amp for the Lineo5 is more for future proofing its flexibilty for additional future volumio products… but, it is a great question for Volumio since in the USA we cannot buy the Lineo5…
I solved this problem with a linear supply bought on aliexpres a dual power supply with two transormers to feed my DAC (12V 5A) and Rivo (5V 5A): A32 - 2.
perhaps You could find it olso in USA. the vantage with this power supply is that olso with my music SSD HD of 2TB I have a more fluid use of music wile before I had to wait a lot to charge new traks from the HD.