8000 character limit on OPENQUERY against a linked server
You can bypass the 8000 character limit of OPENQUERY by utilizing EXECUTE AT, as follows:

DECLARE @myStatement VARCHAR(MAX)
SET @myStatement = 'SELECT * FROM TABLE WHERE CHARACTERS.... ' -- Imagine that's longer than 8000 characters

EXECUTE (@myStatement) AT LinkedServerName


In order to make sure this doesn't throw an error, you need to enable the RPC OUT option on the linked server, by issuing the following command:

EXEC master.dbo.sp_serveroption @server=N'LinkedServerName', @optname=N'rpc out', @optvalue=N'true'


Or enabling it within the GUI: