How to use update-alternatives per user

Is there any way to use update-alternative "user wide" ? I mean that it would be great to set preferences per user.

Does Debian provide some tools for that?

Yes, you can absolutely use update-alternatives for yourself. For example, I have different LLVM versions installed under ~/.local/llvm-VERSION. I can install binary links into ~/.local/bin (which is in my $PATH) like this:

alias update-my-alternatives='update-alternatives --altdir ~/.local/etc/alternatives --admindir ~/.local/var/lib/alternatives'
mkdir -p ~/.local/var/lib/alternatives ~/.local/etc/alternatives
version=3.9.0
slaves=""
for b in llvm-${version}/bin/*; do \
    slaves+=" --slave $HOME/.local/bin/$(basename $b) $(basename $b) $(readlink -f $b)" \
done
update-my-alternatives --install $HOME/.local/bin/llvm-config llvm $(readlink -f $(dirname $b)/llvm-config) ${version//./0} ${slaves}

I can repeat the last command for new versions and use update-my-alternatives --config llvm to choose between versions.

If you want to use the pre-existing system alternatives, you could possibly copy over all the files in /var/lib/alternatives to ~/.local/var/lib/alternatives and change all of the system paths in the first section to be user paths (e.g. change /usr to /home/username/.local).

Users who don't want to use the system default for an application that uses the alternatives (and an alternate is indeed installed) can always simply use either the correct name or full path for the non-default alternative or set up an alias overruling the symbolic link.