I've dreamt of governments hiring devs with promises of full time OSS work. It _might_ get some people over the lower salaries of government work. But I overheard a state CIO once say "We configure, we don't create".
That's to say nothing about opinions of open source that rival early 2000s Microsoft.
For old ass critical software and hardware, the org can always have a backlog of hardware and contingency plans (paying someone to fix the hardware, paying someone to create a fully certified and modern solution..) for when they start running out of parts.