I have installed clang-12 OK and can compiler and link and run with it.
But when I try the analogous command for version 13
sudo apt-get install clang-13 lldb-13 lld-13 --install-suggests
I just get
Package clang-13 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source.
https://apt.llvm.org/ suggests that version 13 (and later) are available
To install just clang, lld and lldb (13 release):
apt-get install clang-13 lldb-13 lld-13
with same messages.
I have also found
https://packages.ubuntu.com/source/impish/llvm-toolchain-13but don't know how to install it.
Any hints for install novice? Thanks.