Install metasploit under ubuntu 20.04+

git clone git://github.com/sstephenson/ruby-build.git ~/.rbenv/plugins/ruby-build
echo 'export PATH="$HOME/.rbenv/plugins/ruby-build/bin:$PATH"' >> ~/.bashrc

# sudo plugin so we can run Metasploit as root with "rbenv sudo msfconsole"
git clone git://github.com/dcarley/rbenv-sudo.git ~/.rbenv/plugins/rbenv-sudo

exec $SHELL

RUBYVERSION=$(wget https://raw.githubusercontent.com/rapid7/metasploit-framework/master/.ruby-version -q -O - )
rbenv install $RUBYVERSION
rbenv global $RUBYVERSION
ruby -v

cd /opt
sudo git clone https://github.com/rapid7/metasploit-framework.git
sudo chown -R `whoami` /opt/metasploit-framework
cd metasploit-framework

cd metasploit-framework

# If using RVM set the default gem set that is create when you navigate in to the folder
rvm --default use ruby-${RUBYVERSION}@metasploit-framework

gem install bundler
bundle install

cd metasploit-framework
sudo bash -c 'for MSF in $(ls msf*); do ln -s /opt/metasploit-framework/$MSF /usr/local/bin/$MSF;done'

msfconsole

https://www.darkoperator.com/installing-metasploit-in-ubunt