[gkiely]

After much digging, here is a way to prevent account changes from the device.

Steps:

1. Settings > Screen time > Use screen time pass code > Enter a different passcode to your main one that you will remember

2. Settings > Screen time > Content & Privacy Restrictions > Scroll down to Account changes > Don’t allow

This prevents account changes from the device, unless you have the second passcode.

This would not prevent a thief who was aware of this (they could attempt to disable screen time then request the second passcode), but it would prevent a pickpocket who happens to see your passcode being entered from changing your iCloud account details.

[BjoernKW]

That's a clever hack. Thanks for finding that out and for sharing this approach.

It's not an optimal solution, but until Apple themselves come up with something better it's at least sufficient to ward off potentially severe consequences from petty crime or crimes of opportunity.