Hi, we have also come across the same issue, using MR42s into 9200L switches, we have only ever used CDP, it shows on some and not on some others which is strange, as soon as we enable LLDP it springs into life.
We never used to have this issue using CDP, the switches have not changed, so I assume maybe something in the Meraki back end?
What would be the fix for this ? we do not want to enable LLDP everywhere.