You have a security principal that works, so that's good. It looks like you just need to construct and specify a security principal template that produces a security principal in the same form.

What is the corresponding email address for user "admin"? Is it admin@myorganism.org?

If so, then this security principal template should work: cn=${uid},dc=myorganism,dc=org

As mentioned in the documentation, LabKey will replace ${uid} with the portion of the user's email address to the left of the @ symbol.

It doesn't look like you need LDAP Search... which is good, because, as I posted earlier, this rarely needed capability is not part of the Community Edition. Don't put any settings into labkey.xml; your LDAP authentication should be configured via the admin web UI only.

Adam