There's 2 ways:
1) Cheating using console
https://ck2.paradoxwikis.com/Console_commands
2) Set Interracial Marriages game rule to Unrestricted and marry dragon.

i see ty for the info

Yes. Start a game as a powerful ruler. Find a unlanded dragon. Cheat move him to your court. Grant him lands. Save and change rulers to play as dragon.

Dragons aren't playable currently because the fun-hating decision to make all the flights theocracys. So you gotta fix that yourself to play a dragon.

you can play them, just need to cheat the government of the heads as feudal or smth, save and play every faction you want. i did it