I’m using network manager with IWD backend. How can I assign myself multiple IP addresses and then use different ones for different services?
Not sure how this would be done with network manager, but if you are configuring an interface with systemd-networkd, then you can just have multiple addresses in the config file: systemd.network(5) — Arch manual pages. this makes an interface reachable using any of the listed addresses on the LAN. You probably want to turn DHCP off if you are doing this though.
iwd is for bringing up wireless interfaces, not assigning IP addresses to them.