Allow local MariaDB/MySQL server to accept external connections

hi - I'm looking for some advice.

We have a client who wants to remotely push data into a DB we have on our server, however, at the minute their detaisl wont connect.

After reading us, i see that we need to have this check (see attached)

However, as we have about 40-45 other sites on this server, Is this a security risk as it seems to be a server-wide setting??

Any advice welcomed

Thanks - Tim