While setting Syncthing back up on a factory wiped Win11 tower I encountered a similar error to this:
“Failed to verify encryption consistency” error= “remote expects to exchange encrypted data, but is configured for plain data”
Thankfully, the solution posted in the aforementioned form post solved my issue. Firefox had in my case automatically pre-inserted a saved password linked to the localholst url. When setting up the folder I had just left it with the pre-inserted password and when attempting to sync; received that error.
The quick fix was to remove the folder password and verify that the “Untrusted“ box on the “Advanced“ page was left unchecked.
Hopefully this help someone out in the future if they encounter this error. Please advise if posted in the wrong category.