

No, if you like mint and cinnamon then why change?
The only reason to change would be if you want a different desktop environment. You could do that with mint or go with a distro that mains a different DE.
Mint is popular and reliable, so only change if you fancy trying something new and are willing to reinstall if its not to your liking.
I used to be on Mint and left it when I decided to move to KDE. It worked fine in mint but I had lots of app duplication in the menus. I also wanted more cutting edge versions.of software so wanted a different district for that. So I switched to OpenSuSE Tumbleweed (a rolling release distro).
If you do want to tinker and try out other distros then you could also play with distros in virtual machines (KVM or Virtualbox) or if you have a desktop get a second harddrive and install a different distro on it. Its easy to dualboot Linux distros (and safest to have separate hard drives so you don’t make mistakes when partitioning).
Regardless of OS version? That sounds like nonsense. Only someone who doesn’t know how Linux works would believe that.
glibc is a fundamental library that underpins Linux. Its been going since the 1980s and is constantly updated and patched.
Similarly the Linux kernel undergoes constant evolution and change.
No one can promise to support Linux regardless of the OS version because by necessity it is constantly changing. Even slow release cycle distros like Debian move forward with each major release. Backwards compatibility is actually a bit of a nightmare on Linux. Ironically it can be easier to get old windows software running on Linux than old Linux software.
People running systems older than glibc 2.31 really should patch and update their systems. That package itself is already 5 years old.