Wound up here with the same issue. Here's how I fixed it...
1. Copy the Mealie appdata folder from Unraid to somewhere you can access it easily
2. Use the following docker image to create a temporary Mealie container (I used Docker Desktop on Windows with WSL):
- nicjohnson145/mealie:0.5.2
3. Mount the folder containing your Mealie data that you copied in step 1 to /app/data in your container. This will basically restore your previous installation settings
4. Log in to temp Mealie and perform a backup
5. Download that backup and use it to migrate as per above link
Hope this helps.