You can just upgrade from 2012 to 2019 the same way you would upgrade from 2012 to 2012 R2. It is a parallel run and it is documented there.
Basically you create a new farm with the same name, same TLS certificate and same service account. Then you run an export script on the old farm, and import the data to the new farm. Both farm are valid and can run in parallel (as long as the token signing certificate is valid). The decision to use one or the other will be done by updating the DNS record (and/or the load balancer configuration if any). You can use a HOSTS file to test it for example.
Have a look and et us know what you think!