Clang 9 on Ubuntu 20 (2022)

 First

sudo apt-get install cmake

sudo apt-get install ninja-build

sudo apt install clang-9

sudo apt install clang-format-12

sudo apt install clang-format (or sudo apt install clang-format-9.0)

$ ninja --version
1.10.0

$ cmake --version
cmake version 3.16.3

$ clang-9 --version

clang version 9.0.1-12 

Target: x86_64-pc-linux-gnu

Thread model: posix

InstalledDir: /usr/bin

$ clang-format --version
clang-format version 10.0.0-4ubuntu1 

End