I evaluated Flutter for my app before deciding to go with Tauri and wrote about it on my blog: https://arboretum.space/blog/why-arboretum-chose-tauri .
The short version is that Flutter's lack of rich text editing solutions at the time made it a non-starter. It's a common problem in the Flutter ecosystem from what I've seen, there's often 0 or only 1 quality package for many "advanced" desktop use cases.
> many "advanced" desktop use cases
I've found that the GUI library I tried (fyne with go) was mobile-first, so some desktop things e.g. file-open dialogs didn't have the functionality I expected (the "dialog" was actually drawn within the same window as the application window). Flutter is mobile first too IIUC.
Outside of Qt, languages like rust and go don't have a good solid desktop GUI development option.