I am using same tool set
Kubernetes (Azure Kubernetes Service) - > Fluent Bit -> Gray Log (OnPrem server)
I am using the below bits and yaml to deploy from github.
Downloaded yaml file and modified hostname , version as per our environment
I am getting [ info] [sp] stream processor started in fluent bit after that I am not getting any response.
Due to firewall issue logs not being sent. You can try the same let me know how it is going