Don't know how much it is wort, but also GDPR applies. So you need a legal basis for processing (at least data from EU citizens). That could well be journalism

Don't know how much it is wort, but also GDPR applies. So you need a legal basis for processing (at least data from EU citizens). That could well be journalism or scientific research, but for anything else it probably should be compatible with the expectation of the users. Fines have been typically rare and low for 'illegal' processing of twitter data. However, also blue sky and any other federating entity could face a legal risk if they do not protect that data reasonably against misuse.