I did also find this [post](How to get SSL cert applied to port 10000 (Webmin + Virtualmin) and 20000 (Usermin) - General Discussion - Virtualmin Community ) and followed Calports guide:
I did also find this [post](How to get SSL cert applied to port 10000 (Webmin + Virtualmin) and 20000 (Usermin) - General Discussion - Virtualmin Community ) and followed Calports guide: