Install nmap if you don't already have it on your Linux computer. Run "sudo apt-get install nmap" on Ubuntu, or "sudo dnf ...
Whether you use an iPhone or an Android, it's easy to share your Wi-Fi so guests don't have to type in the password.
You can use public Wi-Fi networks safely if you stick to networks you know, visit secure sites, turn off AirDrop and File Sharing, or use a VPN.