Besides JavaFX[1] are there any free, open-source, object-oriented, event-driven, cross-platform, native GUI frameworks that allow for keyboard-accessible UIs? Preferably using a modern language such as Go.

When I developed KeenWrite[2] over 12 years ago, I chose JavaFX because it was (a) bundled with Java; and (b) ran on Linux, Mac, and Windows. JavaFX was later ripped out of Java, to my chagrin, forcing a number of technical contortions.

[1]: Not free on Windows due to Microsoft's $500 cert signing process.

[2]: https://keenwrite.com/