List which shell is used

readlink -f $(which sh)

echo "$BASH_VERSION"

The chsh command changes the default shell only for the user who executes the command. If you want to change the default shell for other users too, so run the following (which will ask for your admin password):

$ sudo chsh -s /usr/local/bin/bash

$ which -a bash
/usr/bin/bash
/bin/bash

/usr/bin/bash –version
GNU bash, version 5.0.17(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2019 Free Software Foundation, Inc.

/bin/bash –version
idem .