Whenever I try to start a game, such as Kirby Air Ride Hack Pack, it shows a black screen and it’s not responding. I even tried uninstalling it and using the git version, but it won’t let me because of an error in building libpng. What’s going on? By the way, I am using it in Manjaro KDE.
I believe I saw another person here mention issues with dolphin-emu. Possibly related Arch bug report? 
Relevant bits for you to try ‘right now’
Disabling LTO stops the coredump on exit for me.
Leaving LTO enabled and switching to clang also stopped the coredump on exit for me
And on the dolphin bug:
dev 5.0-19776 and it worked
Dolphin emulator used to work on my manjaro PC, but after some update maybe a couple months back it stopped working no matter how much I uninstalled it, reinstalled it, reset settings and so on.
If I loaded any game it would just blackscreen.
I just got an update to dolphin emu today on manjaro that fixed my issues! So you should see if the update fixes it for you!