Unity Android build not working correctly on some devices

Hello, I recently put up an App on the Play Store (can be seen here: https://play.google.com/store/apps/details?id=com.LPD.FlippyBird)

Up until now, I thought everything worked fine. The Editor looked like it was supposed to and on my A20 it also looked like the Editor.

My friend then downloaded and ran the app on his S9, and the app completely bugged it. It looks to me like everything in the scene isn't loading except for the canvas. It also seems like the screen isn't refreshing like it should, so wherever something moves on the canvas, everywhere it has been stays in the background, much like how it used to be on windows when applications would load up.

Here's how it's supposed to look (and how it looks on my A20):

Here's how it looks on my friend's device (Galaxy S9):

Please help! Thank you!

 

Update: it's happened on a One Plus 7 Pro now. Same exact thing

 

Update: similar bug occurred on Galaxy S5, except the 3D assets loaded and the canvas worked fine. The 3D assets updated to look like how the bug example I provided looked for the canvas

 

update: it was a clear flags issue. The solution was to set clear flags to solid color. Based on the description of clear flags, this solution doesn't make any sense, but it's what worked.