Hello @Plimsoll and Happy New Year! 
Following the Commission Implementing Regulation (EU) 2016/1928 on determination of cargo carried, which is still in force, the definition of ‘General cargo ship’ is as follows.
General cargo ship means a ship with a multi-deck or single-deck hull designed primarily for the carriage of general cargo excluding specialized dry cargo ships, which are not included in the calculation of reference lines for general cargo ships, namely livestock carrier, barge carrier, heavy load carrier, yacht carrier, nuclear fuel carrier.
However, it would not be surprising if the scope of the application expands, especially considering that, starting January 1, 2025, the EU MRV Regulation will also encounter general cargo ships with a gross tonnage between 400 and 5,000 (Regulation (EU) 2023/957). Still, I understand that in order to facilitate such expansion, relevant reference lines should be developed first.
References:
- CELEX_32016R1928_EN_TXT.pdf (324.0 KB)
- CELEX_32023R0957_EN_TXT (1).pdf (478.1 KB)