"Everything seems to be running on stock Ubuntu VMs nowadays" - More of different linux variants actually. Amazon, for instance, provides their own version cal

"Everything seems to be running on stock Ubuntu VMs nowadays" - More of different linux variants actually. Amazon, for instance, provides their own version called "Amazon Linux" which is based on RHEL/CentOS for their aws servers. I've also seen many use Debian for their servers (In fact, Debian/Ubuntu doesn't differ much technically on the server side, but Debian's simplicity and FOSS-friendliness drives many towards it).