Yeah definitely a change as to what was listed in the port map.
I have a Netgear WNDR3400v2 as a dumb AP as well that has a the identical switch0 layout as what you have on your C7 v5. It was originally using eth0.2 for WAN and eth0.1 for LAN. Here is my /etc/config/network for it:
config interface 'loopback'
option ifname 'lo'
option proto 'static'
option ipaddr '127.0.0.1'
option netmask '255.0.0.0'
config globals 'globals'
option ula_prefix 'fd44:ca90:824c::/48'
config interface 'lan'
option type 'bridge'
option proto 'static'
option netmask '255.255.255.0'
option ipaddr '192.168.1.70'
option gateway '192.168.1.1'
option delegate '0'
option dns '192.168.1.1'
option _orig_ifname 'eth0.1'
option _orig_bridge 'true'
option ifname 'eth0'
option name 'switch0'
option reset '1'
option enable_vlan '1'
option device 'switch0'
option vlan '1'
option ports '0 1 2 3 4 5'
Note: I have deleted the WAN/WAN6 interface as well as the VLAN (id 2) for them on the switch as well. I think the
option _orig_ifname 'eth0.1' and
option _orig_bridge '1' are missing from the configuration in the OP of your /etc/config/network. However, these should only should only have been used by LuCI to to keep previous information across edits. The
delegate '0' option is just telling it not to use built-in IPv6 on the interface. All the ports are untagged including the CPU port (eth0), because we are only using 1 VLAN.
Here is a little description about the tagging of the ports and interfaces. First off, the interface (CPU eth0) should always be either tagged or untagged, never off if you want to be able to reach SSH or LuCI in OpenWRT through that specified VLAN. If you have one interface that controls multiple ports, like in your case (eth0), and those ports are distributed across multiple VLANs, which is the default configuration, WAN for VLAN id 2 (eth0.2) and LAN for VLAN id1 (eth0.1), the interface should be tagged. If all the ports controlled by the interface are on the same VLAN and do not span multiple VLANs there is no need to tag that interface. Which is how you want your dumb AP to be, all ports on VLAN id 1, thus no need have the CPU (eth0) tagged, leaving it untagged.
I suggest as @trendy suggested as starting fresh at this point and resetting to factory defaults and just setting up and testing with LAN ports leaving the WAN port and switch tagging configuration to the end of the configuration after a save.
After a fresh start, disable the WAN/WAN6 (not delete for the time being), also uncheck the 'bring up on boot option'. Then configure the LAN, set a static IP, gateway and DNS to the router, with a matching netmask. Also in the LAN interface check 'ignore interface' under DHCP. If you are using wireless set that up then bridge it to LAN.
Then disable your services: firewall, odhcp, dnsmasq
(You can always go back and enable dnsmasq and add 188.8.131.52 to the DNS servers for failsafe later)
Back up the router configuration at this point then reboot the router.
Using the LAN ports only test and see if your dumb AP is working as it should.