Does anyone know how to upload SMB logs to ELK? Is it even possible?
What are you looking for specifically?
smbd.log is part of syslog messages, you can include audit as well.
From syslog to ELK shouldnt be an issue 
Graylog uses ELK as its backend, IIRC. Set that up as a custom app using YAML, point the syslog output to that, and I’d expect it will do what you want, with a pretty GUI to boot.