If you go to whatismyipaddress.com, is the IP address you see there the same your router tells you as your WAN or public address?

And if it is different, is your routers public address somewhere between 100.64.0.0 and 100.127.255.255?

Could you please try to do a ping for 8.8.8.8?

Could you please try to do a ping for 8.8.8.8?

TL-SG2008 v3 from TP link, while it is managed, you could simply deactivate all extras

Not exactly what I wanted to achieve with my idea, but it seems that my idea is not feasible. But thank you, for your answer.

It depends on your requirements.

If you only need a lot of ports, all on the same subnet, an unmanaged switch will do.

If you are planing to use VLANs or other features a managed switch will come with, then you should get a managed one, if it is within your budget.