Observability in a Multi-Cloud Environment?

We're running on AWS and GCP, and, honestly, with all the microservices we have now, it's getting kinda tough. We can see what's going on inside each cloud, sure, but when something breaks or we need to figure out how a request went through everything, it's a real headache. Has anyone managed to get a handle on observability across different clouds? What tools or methods actually worked for you, and what was the hardest part?