Interestingly regarding guijs, we are able to talk with the backend via the node server that was built for it. And because of this, its very easy to just pack the tauri app with a script that runs that server when the user opens the app on their computer. You can side load any kind of executable with your tauri app in this way; so if I built a go/rust server app and compile it into an executable, I could glue it to the tauri app to deal with whatever backend stuff I would need.
You said this has been particularly tested with Vue and Quasar, is there any reason to worry that others have not been as well tested?
I'm loving Svelte, has many of the same goals as Tauri, tiny app size as well as very high performance. And Smelte is seeming like their version of Quasar. Any reasons to worry about running into an unresolvable issue?
We've tested as many frontend frameworks as we could; as far as we've seen thus far, so long as you can bundle whatever it is you want to put into the webview it should work. We do have a svelte example in our examples repo along with examples from transpile to JS languages like Mint, ReasonML and Dart/Flutter.