Yet, it's curious that you compare Slint to LVGL/Flutter/Electron (I don't know about Qt) when none of them have this intrusive requirement.
--- >What's intrusive about it?
(a) Display the AboutSlint widget in an "About" screen or dialog that is accessible from the top level menu of the Application.
(b) Display the Slint attribution badge on a public webpage, where the binaries of your Application can be downloaded from, in such a way that it can be easily found by any visitor to that page.
(c) You may not remove or alter any license notices (including copyright notices, disclaimers of warranty, or limitations of liability) contained within the source code form of the Software.
(d) You allow SixtyFPS to use your Application on the website and in advertising materials of SixtyFPS as a reference and to display your logo and trademark for this purpose.
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Please don't pretend like a/b/d aren't big asks by saying "you wont even provide attribution?"