Configure OpenWrt as old fashion HUB like

I would like to configure the OpenWRT as an old fashion Hub like, i.e. to sniff traffic without using IPv4, just connecting the RJ-45.
Would you please help me?

there's a package mirroring option somewhere, at least in openwrt 19....

Thank you very much. I've found this:, I'll try it!

sounds like nftables can also do that:

Great, thanks @Pico, I'll test that too!