sudo apt install dos2unix
dos2unix installer.sh
chmod +x installer.sh
sudo bash installer.sh

if you got error frontend/frontend/.next
just cd  to frontend directory and run pnpm install

for pnpm root problem script assign new user then check permissions ownership so let the script in first install complete it may take time in firewall and ports adjustement step 
check dev documentation 
https://docs.mash3div.com/#virtualmin-setup