This post will explain how to install the Bourne-Again-Shell version 5.1 for Linux (and Unix), independend of the CPU architecture.
I expect you to have the common build tools already installed.
This post is an update of Bash 5.0 installation for Linux
wget http://ftp.gnu.org/gnu/bash/bash-5.1.tar.gz
tar xf bash-5.0.tar.gz
cd bash-5.1
./configure
make
sudo make install
and finally, to run sh