Hi,
ArchLinux is using networkd (a systemd component). To configure static WiFi addresses, go to the folder: /etc/systemd/network and modify the file: wlan0.network similarly to:
[root@repeater-146820 /]# cd /etc/systemd/network/
[root@repeater-146820 network]# ls
eth0.network wlan0.network
[root@repeater-146820 network]# cat wlan0.network
[Match]
Name=wlan0
[Network]
DHCP=no
DNS=127.0.0.1
Address=192.168.124.82/24
Gateway=192.168.124.1
73, David KB4FXC