Currently it's ~86% according to caniuse.com. I think it's still a bit low to be used comfortably.

This means that it won't work in a builtin browser of a smartphone made 5 years ago.

I think that average quality websites made for public Internet should use only features that have been supported at least for 5 years in major browsers including mobile. And a high quality site must be usable in 10-years old browser.

It doesn't work on iOS 13 only grid gap works