Short answer
There is no universal distance this site should present as safe. Use distance as one input.
Why exact numbers can mislead
Explain that wall construction and wiring paths vary, and a generic number cannot see behind the wall.
A better decision sequence
Choose another location if possible; name the object; check wall condition; scan with caution; review device proximity; stop on uncertainty.
Lower-risk examples without permission language
Low-consequence decor far from visible devices may continue to planning only after checks; those checks do not clear a drilling location.
When distance does not help
Electrical alerts, damp walls, bathrooms/kitchens, heavy objects, overhead locations, unknown wall type, and old repair zones.
Stop rules
Stop when the reader is looking for a magic distance, the wall is near electrical/plumbing/gas/water risk, or the object/failure consequence is more than cosmetic.