Actually, no, it doesnt apply to twitter right now (turnover and market cap is too low). But EC can assign status anyway following market investigation.
It absolutely does apply to Youtube (finally some way to challenge youtube!), but im not sure how that affects the use of youtube-dl.
The DMA covers ten core platform services:
- online intermediation services;
- online search engines;
- online social networking services;
- video-sharing platform services;
- number-independent interpersonal communication services;
- operating systems;
- cloud computing services;
- advertising services;
- web browsers;
- virtual assistants.