Ah, just as I post my method of creating a shortcut with an icon of my choice on the iPhone home screen - which I demonstrated with Firefox - along comes a browser that allows a choice of icons out-of-the-box!
Here’s how I “changed” an app’s home screen icon on iPhone. I’m so OCD that I want my home screen dock icons (the tray at the bottom) to be all of the same colour! Actually, changing an icon is not possible, but creating a new shortcut with an icon of my choice is!
I just spent hours trying to figure out and fix a Windows 10 machine that was taking 100% disk, 100% RAM and about 50% CPU with abolutely nothing running. Of course, I initially blamed the user... then, a misbihaving (hidden, background) app... then, malware / virus... the, a runaway Windows Defender... then, a hard disk / hardware failure... but ultimately discovering the culprit is - drum roll - Microsoft Windows itself! As usual!