Not really, no.

Cloud Run implements the Knative API, so you can actually take it away and run it on any Kubernetes cluster anywhere on a cloud or in your datacenter.

Doesn't that require Istio and a few other things as well? I wouldn't wish Istio configuration and maintenance on anyone but the larger shops/teams. You might not be technically locked in, but not everyone can afford to dedicate the attention to tuning and maintaining Istio.

Source: at mid-sized company who has Istio in the stack.

Knative just needs a gateway (LB); not a full mesh. Istio is the default option. Alternatively you can use Gloo, Ambassador or something specifically built for Knative such as Kourier.

Vendor lock-in does not come from using GKE/EKS/AKS or derivatives.

What ends up happening is that your application consumes services (storage, analytics, etc.). You start using those services from the cloud provider, which makes sense as long as it is the right thing for your business (aligns w/ your cloud-native blueprint).

Kubernetes, by itself, is cloud-provider agnostic.