The MX4300 is indeed DSA.
It looks more like no switch at all (like on x86).
- The toh says IPQ807x has no DSA support
- This comment (old, 2022) says the driver is faking independent network cards.
- The MX4300 Luci UI reports them as "Ethernet adapters" rather than "switch ports"
I agree the MX4300 is definitely not swconfig (no switch configuration in /etc/config/network).
The reason this matters to me is because I am trying to correctly configure VLANs and trunk ports and the system being DSA/swconfig/no-switch affects the ports and names used to configure bridge devices and such.