Well, that is interesting. That is a feature that I did not even know existed and I have been using SDRuno for over 2 years now. It is a feature that I use on the KiwiSDRs so, you have my attention. If it follows SDRuno's main clock setting then:
Main Panel -> Settings -> Misc -> "Show UTC Time".
It's on page 15 of the manual. I cannot confirm at this time as I have already rolled over 00:00 UTC.