It's mainly regex lookbehind, but there can also be many other side effects of using Safari over Chrome or Firefox (such as page zooming issues and other render

It's mainly regex lookbehind, but there can also be many other side effects of using Safari over Chrome or Firefox (such as page zooming issues and other rendering stuff, and their disappointing lack of good support for PWAs). The regex lookbehind support problem is the main blocker, though; and really, it should have been implemented _ages_ ago (the WebKit issue for it was made in 2017, and has been open ever since). It's a shame that Safari's the only modern browser which lacks the support for it!