I'm not Brazilian, so if you have a translator, I'd recommend using it.

DeviantArt, Fandom Wiki, and Tumblr (the last in which is the ULTIMATE hub for UTMV (Undertale AU fan content), which is a big deal) are the spaces where you can create an AU, though Reddit can also be used to pitch ideas.

The best option is to start with a form of digital art (Be it pixel art or digital art) and then do one of four things. There are other options in this community, but for what you're trying to make, there are four primary options:

• The fanart route: Simply have a series of arts depicting the AU and its characters, an approach UNDERFELL originally took and was also taken by OUTERTALE.

• The Web-comic route: The ol' reliable; A series of comics, be it an episodic series like Hand plates or Fellswap X or a bunch of comic shenanigans like with The Bad sanses or Min-play Underswap, though those are more akin to fanarts. Comics often have dialogue that needs to be written and multiple panels that show different perspectives and moments in the AU.

• The Fangame route: It is nearly mandatory to do individual sprites (small artworks) and learn coding if you want to make a Brazillian UNDERTALE fangame. TS! Underswap, La Jupo Vania, The Thanatos duology and Undertale Yellow all fall under this umbrella. If you're going to do a fangame, I'd use gamejolt for this rather than Tumblr or Deviantart.

• The Animation route: A full blown animation series of the AU, something only few big AUs have ever done, and for good reason... Xtale is the primary example of this path. If you manage to make a masterpiece of an AU animation series with this premise, I commend you. This is obviously where Youtube becomes the optimal website for sending this stuff.

If this is gonna be an aesthetic AU like Outertale, you can kinda just copy-paste UNDERTALE's lore and just change minor stuff to better fit the concept. If it's gonna be a full blown thing like TS! Underswap, a new (although maybe familiar) story is going to be optimal.

Ok, ima amke animations bc i dont ahve any social accounts(exept for you tube)

Also im fluent english only my grammar is bad

Also my au name is Brasiltale(n the "Brasil" isint a typo, here in Brazil we call our country "Brasil"

So imm a good coder but im not soo good at making sprites