I know that Troy posted about the blank rectangles that should be app.
I’ve tried his suggested workaround ie launching from launch manager.
It worked for a while in as much the icon was there but empty, then it just disappeared again.
I get the same thing with Sincler, there’s another blank there also can’t seem to determine what that one is.
I also have a 4K everything is listed and working fine on that, regret buying the 4K Max.
I have a max and don’t have any missing icons but it depends on the app developer and if he coded the app for the new Fire OS. What I did was switch to the Wolf Launcher and the launcher manager. All my icons show in there. If some still don’t show then at least you can give the Icon a name in the modification settings.
You’re looking for the sideload launcher app. Many side loaded apps will not display the icons correctly but they are still there. The sideload launcher just allows you to see them correctly.