Flutter looks nice, but it's dart.

In a sane world we would already have webviews on all platforms and the problem mostly solved for client applications. But there's a lot of forces at work that want to artificially suppress web UI. Chromium doesn't have webview on desktop platforms, but Microsoft's chromium edge does. Apple puts in their special restrictions making up rules for any app that uses wkwebview.

Nobody with the power wants to make webUI universally deployable.

At the end of the day you choose one that you'll actually deploy something with. There's no more right or wrong in UI, it's can you get to the goal of deploying a functional app or not.