I suppose this is about the device https://devices.ubuntu-touch.io/device/joyeuse not having a Focal release available (if this is about the Note 9 Pro version).

Unfortunately, the porter has discontinued support and the device is no longer maintained. There has been some initial work on this done to support Focal, but never finished.

So at this moment you options are to:

stick with the outdated UT Xenial, try Droidian instead, or use Android, e.g. Lineage OS v20

Or you can revert to the stock ROM for sure.