Copy Data Activity failed on Upsert

This is a valid solution, and will solve my issue, in the meanwhile I figured out what was wrong.

I was also providing a full column mapping in the mapping section. When doing that dynamically, you need to add the type conversion section in the dynamic mapping explicitly:

"translator": {
  "type": "TabularTranslator",
  "mappings": [ ... from your config table ... ],
  "typeConversion": true,
  "typeConversionSettings": {
    "allowDataTruncation": false,
    "treatBooleanAsNumber": false
  }
}