I remember that bike. It stuck out because my Advent drivetrain - with the 11-46T steel cluster - is on my own Mongoose Envoy. I did the long cage version of the derailleur. It works splendidly... but you know that for yourself
.
Not so long ago I scored an 11-48T steel Advent X system on clearance at California Ebike (they are still on sale there). I ended up replacing my 12-50T Box 2 XW derailleur on my Bullitt and I actually get better performance out of it than the much more-expensive Box system (with a Box 1 shifter no less). On a tip from a Youtuber I put an 11s chain on that 10s system and it worked beautifully. 11s chains are the same width internally but a hair narrower externally. The idea is they run silently and when I put it on it was like a minor miracle. I never realized how much chain noise there normally is until I did this (its been awhile since I had a Gates belt so I'd forgotten that part).
In the last few years Microshift has made a concerted effort to leave their old reputation behind. It started with the 9s Advent system, and continued with the Advent X. Both my Advent and Advent X were super easy to adjust at install and neither has needed any further tinkering. It helped maybe to use the Microshift install videos which have very different - but really easy - derailleur adjustment instructions.
Their clusters are a marvel for mid drive durability. 1-pc steel if you want that version. Pinned together all over the place so no worries about tacos, with bolsters in between the big ones to further brace them. Even the two smallest cogs are steel which is unusual. In the pics below, the first one is 10s Advent X and the second is 9s Advent. These are like $39 cassettes too so MUCH better choice than Shimano HG400 for example, which used to be my favorite 9s mid-drive cluster.
View attachment 153833View attachment 153836
My Advent X experience is not a knock on Box Components. I have several Box 2 setups and the only reason it didn't work on my new Bullitt is its super short chainstays coupled to a BBSHD. Not enough room to maneuver, and I gained a couple extra usable gears thanks to the slightly different teeth and closer cog spacing. Box would be overkill by a wide margin for an Aventon.