Actually, the Emoluments Clause specifically states that the President shall not receive any other emolument from the US Government:
The President shall, at stated Times, receive for his Services, a Compensation, which shall neither be increased nor diminished during the Period for which he shall have been elected, and he shall not receive within that Period any other Emolument from the United States, or any of them. - Article II Section I
If that’s the extent of the clause, you are on target.
Anyway, doesn't President Trump not accept his salary but donate it?
There are more than one emoluments clauses. The Foreign Emoluments Clause, Article I, Section 9, Clause 8, also called the Title of Nobility Clause is probably the one used in the lawsuit.
Art I, Sec 8
“8: No Title of Nobility shall be granted by the United States: And no Person holding any Office of Profit or Trust under them, shall, without the Consent of the Congress, accept of any present, Emolument, Office, or Title, of any kind whatever, from any King, Prince, or foreign State.”