I also am experiencing this issue where all of my saved data for my Character information has been erased. This includes when connecting to realms via Microsoft Account. Am currently playing on a Switch (Bedrock Edition). In addition to this, All the things i have previously downloaded in the store and through the holiday event are now missing.
I have gone through and recreated my character 3 times now and three times when i come back and log in, my character information is missing. This has only started AFTER the last update 1.16.210.
This is now happening on Switch after last version update 1.16.210
Custom Skins that were there were replaced with Steve or Alex
Updating the Skins does not get saved after closing out of the game.