Theoretically a lot of this spend also comes with support contracts, and I expect even moving to a Linux flavor would have to, as well. The last public outfit I worked in was using RHEL as their path forward from big iron AIX, and even that only on the very particular piece of infrastructure I was working on, since it was a Windows shop. The licensing and support was definitely a better experience than M$, but I expect you'd be hard pressed to find a government who'd sign off on just deploying Mint on 5000 workstations and calling it a day. There's also the enormous inertia of Windows sysadmins who only know how to do MDM and group policy and shit in AD with a GUI.
Looking forward to the arch libertarians plucking out their own eyes in protest. Less looking forward to the AI psychosis victims maiming their families.
Yesss, put this poison in my veins!