Hate that they recently implemented PWAs, but didn't bother making sure the icon for the site worked, so all PWAs have the genetic Firefox icon. The most valuable feature of PWAs is to identify a tab as a standalone app and there's no fix for this in sight.
I just tried it out with this page, and it gets the HN icon for me. I am on Nightly and on Linux, so possibly this is an actual bug you're running into, but no fix in sight might be too pessimistic. But definitely worth reporting otherewise.
Keep in mind that just because it works for me, that doesn't mean that you're not running into a bug that I'm not, so I can't make any promises about it actually being fixed for you :)
