I want to do this very same thing with a GL-MT300N-V2, (that is, connect a wired device to my wifi network, bridged as if it were connected directly with a wire (ie, no firewall, no NAT, the gateway should see it’s actual MAC, etc) and without creating another AP network, I don’t need my wifi ‘extended’ I just need to connect a wired device to it). However, when I select ‘Extender’ mode my arpwatch goes crazy as the GL-MT300N starts to ARP announce as basically every other device on my network (including the gateway):

12/19/2022 10:39:12 AM Flip flop 94-83-C4-1F-9D-6D takes other’s IP: 10.0.10.202
12/19/2022 10:39:13 AM Flip flop 94-83-C4-1F-9D-6D takes other’s IP: 10.0.53.5
12/19/2022 10:39:15 AM Flip flop 94-83-C4-1F-9D-6D takes other’s IP: 10.0.10.201
12/19/2022 10:39:15 AM Flip flop 94-83-C4-1F-9D-6D takes other’s IP: 10.0.4.12
12/19/2022 10:39:16 AM Flip flop 94-83-C4-1F-9D-6D takes other’s IP: 10.0.4.8
12/19/2022 10:39:16 AM Flip flop 94-83-C4-1F-9D-6D takes other’s IP: 10.0.3.15
12/19/2022 10:39:16 AM Flip flop 94-83-C4-1F-9D-6D takes other’s IP: 10.0.4.6
12/19/2022 10:39:16 AM Flip flop 94-83-C4-1F-9D-6D takes other’s IP: 10.0.4.7
12/19/2022 10:39:16 AM Flip flop 94-83-C4-1F-9D-6D takes other’s IP: 10.0.3.12
12/19/2022 10:39:16 AM Flip flop 94-83-C4-1F-9D-6D takes other’s IP: 10.0.10.203
12/19/2022 10:39:16 AM Flip flop 94-83-C4-1F-9D-6D takes other’s IP: 10.0.3.19
12/19/2022 10:39:16 AM Flip flop 94-83-C4-1F-9D-6D takes other’s IP: 10.0.10.204
12/19/2022 10:39:17 AM Flip flop 94-83-C4-1F-9D-6D takes other’s IP: 10.0.0.1
etc…

Am I doing something wrong? I also tried ‘WDS’ mode, not sure what the difference is, but that doesn’t seem to do the same thing (tries to take over the IP of every other device…)