OS packages are generally there to be a dependency of some other package. They are stable, but out of date, as they don’t increase major versions after the OS is released.

Erlang Solutions maintains up to date packages: Erlang and Elixir Packages Download - Erlang Solutions
Packages are much more important for Erlang than for Elixir. Once you have an up to date Erlang, you can simply download Elixir from https://elixir-lang.org/
ASDF is great for managing app dependencies: Using ASDF with Elixir and Phoenix
It will take a while to compile Erlang, though, so if your machine doesn’t have a lot of resources, you can use the OS package for Erlang and use ASDF for Elixir.

That link also clearly says:

If your distribution contains an old Elixir/Erlang version, see the sections below for installing Elixir/Erlang from version managers or from source.

So, follow that sentence and use asdf.

To be honest, in 15 years I have not yet the luxury of only needing a single version of a language installed.

And those versions that have been required by the projects always have been either behind or newer than the systems version.

So unless you are on nixOS, using asdf-vm for everything is a very good advice.

I wouldn’t trust distro packagers to give you the lastest version of software in general. Can you use a different installer like adsf? The hw itself supports higher versions (elixir-nerves distros are up to date)