Hi there!
I recently came across the issue, that to specify GHES one needs to both supply the core API endpoint and the upload API.
However the docs for uploading release assets state the the upload URL is specified in the Release object - so either returned while creating the release or obtainable by fetching the release.
Could the UploadRelease() be implemented in a way that it takes a RepositoryRelease instead of owner, repo and id?
This would remove the need to setup the Upload API endpoint in Client.WithEnterpriseURLs() at all.
Best regards,
Andre