Yes, you can play Only Up! on mobile devices, but there are some points to note:
Android: There are some unofficial ports of Only Up! for Android. You can download them from some third-party app download platforms, such as Duoduo Software Station, 289 Mobile Games Network, Xiazaiba. However, these versions may have security risks.
iOS: At present, there is no official Only Up! version for iOS on the App Store. It's not recommended to download unofficial versions from third-party platforms because of potential security threats. It's advisable to wait for the official release.
Streaming Services: You can also try to play Only Up! on mobile via game streaming services like GeForce Now or Steam Link. But this requires purchasing the game on a gaming platform like Steam and paying for the streaming service. There may also be limitations on FPS, daily playtime, etc.