Finding a MAC address of a device on the network

You need to do an ARP scan which means Address Resolution Protocol, which is a layer below IP addresses on the OSI model

you can do this by using nmap or pinging the device

sudo nmap -PR -sn 192.168.1.0/24

or for when there is no DHCP or DNS server in the loop:

ping -c 1 192.168.1.64

ip neighbor show