If you're doing Python, you may have a look at Kivy, it's not native UI, but it's quite nice, and can be run on all major platforms. On Android it's not perfect though, as you have to deal with bigger starting time (Python interpreter needs to be launched), and there is an impact on performances.
On desktop it's working really well (again, if you're OK with non native UI).
The Kivy ecosystem offers many neat things like PyJNIus to access Java class (and thus Android API) from Python, or Plyer for high level cross platform access to features like notification, vibration or GPS.
An other uncommon choice which can be interesting (and has been discussed recently here), is using Godot for UI.
The Kivy ecosystem offers many neat things like PyJNIus to access Java class (and thus Android API) from Python, or Plyer for high level cross platform access to features like notification, vibration or GPS.
An other uncommon choice which can be interesting (and has been discussed recently here), is using Godot for UI.