How do I check if text values are in a different list and count the values not in this list

I have 2 lists with different clients. One List is from 2020 and one list is from 2021. I want to check how many new clients booked in 2021.

My approach would be to check if the Name of the client in 2021 is found in the 2020 list.

How do I achive this?

I've made an example sheet to make it a bit clearer.

For a easier understanding I sorted the clients list. The original sheet is random mixed.

Thanks a lot