[phil294]

I have built this here https://github.com/phil294/vimium-everywhere, and it works okay-ish performance-wise. For example, generating the click hints on this thread on Firefox takes (including FF's UI elements) takes one second, perhaps less on a fast machine. I use it on a daily basis. It needed a lot of optimizations to get to that point though. There are also a few alternatives listed.

And almost all applications support at-spi once you set some env vars! Including electron apps etc., see the readme