The CSR generator needs to support SAN's as it does in the SMA v8.1
I am speaking from SDA v5.1 perspective. I do not know if SDA v6.0 has already resolved this. The SMA v8.1 resolves this issue.
The issue is described in this knowledge base article:
https://support.quest.com/kace-systems-deployment-appliance/kb/230041/error-net-err_cert_common_name_invalid-certificate-error-on-browser-230041-
The SSL certificate signing request feature needs to support the entry of SAN's.

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Patrick commented
This is still an issue with the SDA (K2000) at the current version (9.0.146).
This first request was made in 2018, almost 5 years and there doesn't appear to be any progress.
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Steven New commented
Still needed for the K2000