Does Nexus Repository log which users up/downloaded which asset?
Can Nexus show it to the Log Viewer by the logging settings?
If the logging setting couldn’t, is there a possible way to know which users up/downloaded the asset?
The user that uploaded an asset is visible in the asset details. You can see those by using the REST API, the search UI, or the browse UI. In theory you could also look at the audit log to see when people uploaded something but that log is more about who accessed your system and I wouldn’t recommend using that to determine what user uploaded an asset.
You can parse the request.log which includes the path and the user.