because web tech isn't really the best solution for quick and dirty UIs.

source: been involved in quick and dirty UIs in a business for the past decade

So what has that decade taught you is the best solution for quick and dirty UIs?

VisualBasic, back in the day.

haven't found a universally good option yet; delphi was close 15 years ago, but the world forgot about it mostly. hoping for WASM+compiled language framework somewhat like this one to fit the bill so I don't have to worry about supporting multiple browsers, multiple browser versions, cross platform support, css...

WASM (language independence) on electron (fixed, controlled browser version) with delphi-like UI designer could work, maybe.

HyperCard.

PowerBuilder, in the EMR industry.

Beeware!

btw. one can also use blazor server-side for business line of applications, which is way more smooth and only needs websockets. so I have no idea which target c# client-side wasm (uno/blazor/whatever) has at the moment, because it simply is too big.

Historically, the companies with large line of business apps that were interested in using JSIL to run C# in the browser were interested specifically because rewriting their software from scratch in Electron was an expensive and time-consuming undertaking. This made it worthwhile to invest in alternatives that would let them reuse existing code. We're talking massive WPF or Silverlight codebases with decades worth of developer time invested that would all go out the window.

The same logic applies now and it's even more compelling since the tooling and performance are better now with the full LLVM WASM toolchain and more robust C# AOT compilation available, vs the dark ages when people had JSIL, Saltarelle and Bridge to choose from.

I'll also note that every major company I'm aware of that made a C# -> Browser move for their tooling eventually regretted it and started shifting away to something better, partly due to platform churn and partly due to how much was outside of their control. Electron may change the equation there enough to be good enough, we'll see - I don't know of any companies that have taken that route yet.