Flutter

Currently developing a small-ish application with ambitious demands on design with Flutter for all desktop platforms and the web.

I'm only a few months in, but so far it’s going very well. Performance is ok, even on the web (much better on native, of course).

My main advise is to develop on native, because it’s a much better experience, but regularly test on web as well, because the Dart compiler for the web behaves very differently than the native one. There were quite a few surprises waiting for me when I tested it after a few weeks of native development.

For database access you're going to need a web service that provides the necessary access, since Web doesn’t allow for anything more direct. You can use that one for native as well, to keep the code uniform across platforms. I don’t recommend writing that service in Dart, there are much more suitable languages available for that.