There's also Sciter, which is supposedly very mature (even more so than Electron), but as it's closed source and released under a mixed licence (there are free and commercial versions), it's not got much traction outside of commercial apps:
OMG, I had never seen Sciter before, All I thought is a lie, ESET, Norton, Avast all were using HTML even before electron exist. I always thought theirs software was made by hand using native APIs and frameworks.