@thibaultamartin @kde @gnome RedHat provides paid support, so does TuxCare. Google, Amazon and pretty much all major tech company contributes financially and via devwork as their own systems operate on Linux.

RedHat develops FreeIPA which is essentially opensource Active Directory. Both AD and FreeIPA are fancy Kerberos wrappers around LDAP.

In most large proprietary software project a small amount of maintainers manage individual components of software. Everything critical in Linux is financially funded somewhere and somehow, anything else has enough passion devs working on it or has heaps of alternatives that can fill it's place is development disappeared.