Version "Linux 2.6" is the same as "Linux Ubuntu 2.6.x" and they maintain support

Nice to greet you and at the same time I would appreciate your collaboration with respect to a question that I present since I do not know if the version of Linux 2.6 is the same as Linux Ubuntu 2.6.x, I would also like to know if both versions are still valid regarding the support provided by the Linux community or if, on the contrary, they are versions that can be considered obsolete.

Any help on this topic is welcome.

Thank you