As Jeff said you are right, the third query is sargable.

The second query shows exactly how SQL Server rewrites your initail query and it's not SARGable because it always converts non-unicode operand to Unicode when two operands does not have the same text data type. So, the solution is to make an explicit conversion and to convert parameter to the data type of the column.

If your column would be an NVARCHAR and your parameter a VARCHAR, the predicate would be SARGable since an implicit conversion is performed against parameter and not against the column.

Of course, the golden rule is to align data types of parameters and columns and if you have to do something for it do it against parameters (functions, arithemtical operations....) and not with columns.