Is AION 2 on mobile?
Not the global version. The AION 2 that launches worldwide on 5 October is a Windows PC game on Steam and PURPLE, and NC has not announced a phone version of it. The AION2 app you can find in the App Store and on Google Play belongs to the separate Korean and Taiwanese service.
NC’s words on it:
“Will AION 2 be on mobile? The global version is currently being developed exclusively for PC platforms.”
So what is the AION2 phone app?
The AION2 apps on the Korean App Store (from NC Corp.), the Taiwanese App Store (from NC Taiwan) and Google Play are the Korean and Taiwanese AION 2, which opened in those regions ahead of the global release and runs on phones as well as PC. In the Korean version even telescopic controllers, the kind that clamp around a phone, have their own setup.
That service is not a way into the global game. The global version can be neither played nor paid for in the Republic of Korea or Taiwan, and no link between accounts or characters on the two sides has been announced. How the versions differ is covered on the Taiwan and Korea versions.

What to play it on instead
A Windows 10 or 11 PC is the only way into the global release. The floor is a GTX 1050 Ti with 4 GB, 8 GB of RAM and 100 GB of space; the full table is on system requirements, and both launchers are walked through on download and install.
If what you want is to play away from a desk, a controller gets part of the way: the game is playable with one, without full support promised for launch, and the Steam Deck is untested. Both are covered on controller and Steam Deck. The PC-only line is about the present, so a phone version of the global game is not ruled out, only unannounced; the platforms page will show it if that changes.