Whoops, turns out that those steps was unnecessary after all.
On the accounts settings page normally the banner picture already has the “X” icon to delete it. I was unable to see the “X” icon because my profile banner was dark so the icon was not visible.
So it is possible to remove (not change) the profile banner. Just not straightforward.
Steps in Lemmy web UI:
Whoops, turns out that those steps was unnecessary after all.
On the accounts settings page normally the banner picture already has the “X” icon to delete it. I was unable to see the “X” icon because my profile banner was dark so the icon was not visible.