Yeah, I've tried a few. I can't quite put my finger on what is wrong, but the ones I've tried just don't feel right.

gnvim¹ was the most usable for me. However, it isn't without problems for my use case. To use my earlier example, switching would mean patching fonts or using overrides in fonts.conf to fake the use of icons in signs.

I did take another look just now², and there a few more for me to try out ;)

¹ https://github.com/vhakulinen/gnvim ² https://github.com/neovim/neovim/wiki/Related-projects