Macbook pro m2 connected to Ethernet cable disables internet to everyone in household

if you are sure the cables have no issues, AND

you have tried a different port on your Ethernet Switch or Router, THEN

by a process of elimination, the USB-C to Ethernet device must be the problem.

I use the Belkin device sold in the Apple store on my MacBook pro M1, and mine has been trouble (and error- ) free.

Have you checked the IP addresses on all of your devices to make sure that you aren't using the same IP address on two devices?

That could be some sort of wonky hardware issue, however...

We have also seen such behavior when the Mac you connect has a Grand Agenda, that eats up almost all of the available bandwidth.

Examples include syncing a photo library, or connecting to File Sync-er services. Third-party file sync-ers are Notorious for ignoring performance issues and scanning all files, both locally and online, non-stop, looking for things that MIGHT need to be updated.

See if the same results are seen in Safe Mode.

Start up your Mac in safe mode - Apple Support

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how about downloading and running this little "discovery" utility, Etrecheck. It fixes nothing. Its only reason the exist is to easily create a report of what your Mac looks like "from the inside". That report is pre-laundered of any personally-identifiable information (even the disk names are withheld to protect the innocent) and can be posted to the forums by following the included directions:

Using EtreCheck to Troubleshoot Potential… - Apple Community

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disable Spotify

and disable all of these:

 File providers:
    OneDrive File Provider - /Applications/OneDrive.app

  Share services:
    Dropzone - /Applications/Dropzone 4.app

  Finder sync extensions:
    OneDrive Finder Integration - /Applications/OneDrive.app
    MEGA Finder Sync - /Applications/MEGAsync.app

NOW try to connect to Ethernet when you are sure ALL are disabled.

¿any difference?

Actual Speed:

The good way to check the actual connection speed USED to be Network Utility, But in Catalina and later,  Apple has deprecated network Utility  and now you have to use a Terminal command to see your actual connection speed. First, you need to know what en number the link is.

based on your Etrecheck report, yours is probably en7

Terminal command:

ifconfig en7 | grep media

with this as my output for 10 Gigabit Ethernet:

media: 10Gbase-T <full-duplex,flow-control>

For ‘regular’ Gigabit Ethernet, you should get this instead:

media: 1000baseT <full-duplex,flow-control>

Errors detected:

To see if an Ethernet link is throwing more than a handful of initial errors, you can use Terminal command:

netstat -I en7

This is the resulting output. Counters are In-packets, In-errors, Out-packets, Out-Errors, Collisions. There should never be more than handful of errors from starting up, and in most cases, NONE.

Name       Mtu   Network       Address            Ipkts Ierrs    Opkts Oerrs  Coll

en7   8163  <Link#4>    00:01:d2:1a:00:dd   696697     0   484301     0     0

en7   8163  grantsmacpr fe80:4::461:ea0d:   696697     -   484301     -     -

en7   8163  192.168.0/23  192.168.0.204     696697     -   484301     -     -

If the link were running beyond its ability to run and be stable, for example it auto-speeded to 10Gb but the cabling could only reliably support 2.5Gb, we would see non-zero errors counts, and errors increasing over time. (and possibly, disconnecting)

Output-errors are errors detected during listening-while-talking operations (Transmitting).

There should NEVER be more than an initial handful at startup, and NEVER during regular operation.

Increasing number of errors indicates your cables are inadequate, mis-wired, or have broken wires in them. You need to repair your cables or test different cables.

speeds over 100 M bits/sec use a modulated signal, which requires all four pairs of wires for data, two pairs for transmit and two pairs for receive. Power-over-Ethernet is not compatible with speeds over 100.

If you run it again, does the number of errors change? how much?

does the number of packets go up by a handful or more?

what speed is the connection running at?