Actually, ETA Prime released a video today and you can install the mod with a 2280 with no issue.

I like the idea of more battery for my ROG Ally, but I'm not giving up my 4Tb 2280 Nvme drive to have it. If that's what it takes to have more battery, I'll pass. I was really looking forward to having more battery. Oh well, I'll just wait for someone to come up with a better battery where you get to keep your 2280 Nvme drive. I have been living with it this long, so waiting a little longer isn't going to hurt me one bit. Drive space trumps more battery for me, and I'm sure I'm not the only one with a huge Steam library that cares about more space for their games. Come up with that Jsaux, and I'll buy it as soon as it hits the shelf.