I am surprised why I needed to find this forum to solve my problem: https://forum.qt.io/post/771711

My protobuf file is as follows:

syntax="proto3";
package edge.connections;
option go_package = "github.com/flowy-live/flowy/genproto/connections;pbconnections";

import "google/protobuf/timestamp.proto";
import "user/user.proto";

message UserConnection {
  user.User connection_user = 1;
  // whether the user is tuned into this contact
  bool tuned_in = 2;
  // whether the connection is tuned into the user
  bool is_tuned_into_me = 3;
  // when the connection was made
  google.protobuf.Timestamp created_at = 4;
}

// Responsible for managing connections between users
// ALL protected
service ConnectionsService {
  rpc FindPeople(FindPeopleRequest) returns (FindPeopleResponse) {}

......goes on and on...

The error I get is `qt.protobuf: No deserializer for type QList<edge::connections::UserConnection>`

My protobuf files are generated fine into my build folder with the proper CMake adjustments (although this took all day for me to figure out with the confusing APIs where `PROTO_INCLUDES` doesn't work). The problem is when I actually make a call, I run into the error above. This is true for other messages as well.

The post I mentioned (https://forum.qt.io/post/771711) saved the day by telling me that I needed `qRegisterProtobufTypes()`. I tried putting it in my main function and that fixed it. I used f1 to see what it is, and there is a note that it should not need to be manually called. I am unsure why any of this information is not in the QtProtobuf docs entrypoint although I know the whole thing is in technical preview.