quoting @omz, new beta release 330018, restored the ability to open external folders on ios13

@ccc Done, thanks and sorry, I always try to not forget it, but, my memory is often overloaded 😢

@PKHG , after you share a gist, the URL is copied to the clipboard. A HUD comes up telling you so. You can use the link item here and paste in the gist's URL.
I made this test gist. Anonymous, but not private settings.
Should would if you click the link, but its not inline as @zrzka points out.