I haven't used Flutter, Ionic or React Native, but I found myself pretty comfortable with Xamarin. I've been using it at work for a fairly big project and I didn't have many issues regarding it.
It also definitely improved over time since I've started working with it (about 4 years ago). All that I've said is mostly related to Xamarin native (Xamarin.iOS and Xamarin.Android), as I didn't touch Xamarin.Forms for a couple of years. Even though it's an amazing tool for prototyping, it really becomes a mess when one wants to customise more the UI, and then it becomes a mess. Besides, it's considerably slower than the native ones.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.