Check if records exists in a table of a different database / LEFT JOIN with 2 databases

I got stuck with the following problem:

I have 2 databases. MS SQL an a local network server and MySQL on a remote server.

I’m synchronizing 2 tables. Now I want to check if records of the local table exists in the remote table.

On the same database I would do it with a LEFT JOIN with the condition of NULL.

How would I do this with 2 tables of 2 different databases?

This is what I have:

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