We are currently attaching the TargetActor from console resources:
https://searchfox.org/mozilla-central/rev/31d8600b73dc85b4cdbabf45ac3f1a9c11700d8e/devtools/server/actors/resources/console-messages.js#42-46
And JS Error in bug 1644186.

But we should avoid doing that. We should narrow down what we really depends on.
At fist sight, it looks like we expect to have the ThreadActor set up in order to get source actor IDs. So that this may depend on bug 1644188, which will surely revisit how we think about Sources from the server side. And hopefully the list of sources is uncoupled from the Thread Actor.