The data center I worked in from 2012 - 2021 as a data center engineer / Linux systems admin started out with classic air cooled vertical racks...In 2017 single-phase immersion cooling was added (horizontal 50U vats using a mineral oil type coolant)...The perhaps single downside was the messiness of working on said servers during hardware upgrades or break/fix...Being the person that handled server recycling when a batch (100s to 1000+) of servers aged out, I always wondered how that would be handled for these oil covered servers.