HPE 1620 VLAN: how to have 1 port visible to all VLANs

I have a HPE 1620 switch connected to an Internet router and various clients. I would like to have the clients on separate VLANs, so they don't "see" each other, but all should have access to the port on which the router is connected.

I tried many different configurations, but none seem to achieve this result. Either the machines have no access to the router, or they all have access to each other probably because they are members of their own VLAN but also of the VLAN ID 1 used for the router port.

How can I achieve this seemingly simple configuration?

Thanks