Just whipped together a quick config to get a new Mikrotik HAP Lite AP connected to Telstra with ether 2,3,4,5 set to be a LAN bridge.
This was using a Telstra Ultimate 4G USB dongle.
/interface bridge
add auto-mac=yes name=bridge-local
/interface ethernet
set [ find default-name=ether1 ] name=ether1-gateway
set [ find default-name=ether2 ] name=ether2-master-local
set [ find default-name=ether3 ] master-port=ether2-master-local name=ether3-slave-local
set [ find default-name=ether4 ] master-port=ether2-master-local name=ether4-slave-local
set [ find default-name=ether5 ] master-port=ether2-master-local name=ether5-repeater-control poe-out=forced-on
/ip pool
add name=dhcp_pool1 ranges=10.8.0.100-10.8.0.200
/ip dhcp-server
add address-pool=dhcp_pool1 disabled=no interface=bridge-local lease-time=10h10m name=dhcp1
/port
set 0 name=usb1
/interface ppp-client
add apn=telstra.internet data-channel=3 disabled=no info-channel=1 name=ppp-out1 port=usb1
/system logging action
set 1 disk-file-name=log
/interface bridge port
add bridge=bridge-local interface=ether2-master-local
add bridge=bridge-local interface=wlan1
/ip address
add address=10.8.0.254/24 interface=bridge-local network=10.8.0.0
/ip dhcp-server network
add address=10.8.0.0/24 gateway=10.8.0.254
/ip dns
set allow-remote-requests=yes servers=8.8.8.8
/ip firewall filter
add action=drop chain=input dst-port=53 in-interface=ppp-out1 log-prefix=”” protocol=udp
/ip firewall nat
add action=masquerade chain=srcnat log-prefix=”” out-interface=ppp-out1 src-address=10.8.0.0/24
/port firmware
set ignore-directip-modem=yes
/system identity
set name=”Mikrotik HAP”