Clank when starting to pedal
Could it simply just be your freehub? Especially on cheaper hubs, the engagement isn’t very good, so you have a lot of time to build up momentum before the freehub actually engages. This will result in a clunking noise.
Since freehub bodies are decently hard to get to, it’s unlikely that the LBS took it apart and relubricated it. If they did, maybe they used oil instead of the factory grease, which would also result in a sharper engagement noise. Perhaps you got degreaser inside the freehub and broke down/thinned the lubricant?
Check that your cassette is properly tightened. That could be another cause.
Make sure your cranks are securely fastened, and that your pedal bearings are in good shape. I’m not sure what else could cause a clunk on only one side.