I also had the same need as you a few months ago. I've successfully migrated using the CoreWCF package and the Microsoft migration guide.
Keep in mind that the project is young and that the project I migrated was simple.
You can find the project on Git here: https://github.com/CoreWCF/CoreWCF and the migration guide here: https://learn.microsoft.com/en-us/dotnet/core/porting/upgrade-assistant-wcf
If your concern is more simple you can think to expose a SOAP service using the SoapCore Nuget package (https://github.com/DigDes/SoapCore).