2 LANS on one switch?

So no reason for operating two VLAN and two IP subnet networks.

Whatever these unknown devices with factory default addresses on the 192.168.x.x network are - very strange in the mid of 2025 new devices don't come by default on DHCP or at least on ZeroConf in case there is no DHCP server active on the network (or an overly-managed network not allowing random MAC addresses without additional network security work).

A possible approach is to configure a PC to the same IP subnet, to a free address, and reconfigure these unknown devices manually.

Difficult to help without more insight. Most devices allow operations as a DHCP client nowadays.

Admitted, I have bought and received some very low-cost DANTE / AES67 devices from mainland China, which came with default RFC1918 192.168.x.x IP addresses preconfigured for commodity, to allow certain out of the box AES67 point-to-point operations out of the box. So had challenged the manufacturer and the chipset-maker to allow some smarter dev-ops. The network we intend to operate these is an unmanaged DANTE network, where Audinate best practices are requesting for DHCP and a fall-back to link local (so called ZeroConf addresses 169.254.0.0/16).

As a temporary workaround, we have statically (fixed) assigned ZeroConf IP addresses to these devices - as long as correct ZeroConf and DCHP client isn't available. This is a hack, just some workaround, not a solution however.

So please provide more insight on the make and model of your unknown devices if you need assistance from the Netgear community side. 

Better contact for assistance would be the unknown device support organisation or the maker or manufacturer of these devices. We're happy to learn more about, and might be able to help.

Regards,

-Kurt.