It's not the only alternative to Electron, but it might be one that offers predictable and repeatable results.
I released a small open source project on HN last week (https://github.com/Fusion/pngsource) and I wrote its backend logic in Go. I built the frontend using Tailwind (https://tailwindcss.com) and DaisyUI (https://daisyui.com) and, using Go compiler flags, I can release the app using both WebView (github.com/webview/webview) (which, yes, does require the host OS' collaboration) and Wails (wails.app) (which also does.)
On Linux/AMD64, the binary's size is 3.7M when building for WebView, and 6.8M when targeting Wails.
The way the app works is I drag/drop files to the UI, magic happens, and I use github.com/ncruces/zenity to prompt the user for a save location.
I cross-compile the apps using xgo (https://github.com/karalabe/xgo)
It's been working pretty well on Linux, Windows, MacOS. I think WebView's approach of limiting the feature set is working well as it feels more "native" than Wails (better refreshes and resize operations for instance)
However, I already have a few tickets reporting that, for instance, the app is displayed as a blank window in some environments. And it's hard to debug remotely, obviously. So, this is where Sciter may be a better option.