With some regularity I get asked if eTap fits on the U.P.. The answer is yes.
Of course that wouldn't be worth its own OPEN Update if there wasn't more to the story, so here it goes. eTap fits on the frame no problem, the bike will shift flawlessly and you'll be very happy. Except eTap poses one big limitation: the way the battery is positioned on the front derailleur, it sits quite close to the rear tire.
To be exact, according to SRAM's tech documentation the clearance from the center plane of the wheel to the inside face of the battery is 20.1mm. If you adhere to the 6mm tire clearance mandated by some rules, that would mean your maximum tire diameter is 28.2mm (2x(20.1-6.0)) or in other words, a standard road tire.
But it seems that SRAM's information is not very accurate, plenty people have assembled 35 and even 40mm tires on an OPEN with eTap, so the official information is off by quite a bit. Partially that's because people decide to flaunt that 6mm rule (I do all the time but of course, I'm irresponsible and I wouldn't want you to end up being like me so "don't try this at home").
So while eTap is completely compatible with the U.P. frame, it's not compatible up to that maximum tire that it can fit. So no possibility for 650Bx47 RoadPlus tires and 650Bx2.0" or even larger GravelPlus set-ups.
There's nothing we can do about it, it has nothing to do with the frame. This is baked into the eTap front derailleur design and applies to any frame you put it on.
You may think to get clever and turn the bike into 1x eTap since the front derailleur then becomes obsolete, but unfortunately the eTap rear derailleur doesn't have a clutch so you would need to figure out something to avoid losing your chain. A small guide is of course an option, and you do have the front derailleur mount available to attach it.
If anybody has done anything creative in this regard, I'd love to see it so let me know.