Like other commenters said, it's just Linux so you can do pretty much anything.
For Qt, the current stack seems to be Kirigami, which is KDE's library for convergent apps. There's also the Mauikit framework, which is built on top of Kirigami (I don't know enough to know the exact differences).
For Gtk, it's libhandy, which adds a few widgets for convergent apps.
There's also a few Electron/Webkit-based apps (especially for UBPorts), which is a nice temporary solution to get an app on the device while there isn't yet a native equivalent.
For Qt, the current stack seems to be Kirigami, which is KDE's library for convergent apps. There's also the Mauikit framework, which is built on top of Kirigami (I don't know enough to know the exact differences).
For Gtk, it's libhandy, which adds a few widgets for convergent apps.
It looks like Flutter doesn't support ARM yet, I found this after a quick search: https://github.com/flutter/flutter/issues/60678
There's also a few Electron/Webkit-based apps (especially for UBPorts), which is a nice temporary solution to get an app on the device while there isn't yet a native equivalent.