Where is the hollow option from wildmount located in character creation? Is it just not an option?

It's considered the same a Supernatural gift and not a player creation option on D&D Beyond.

If you have need, you can create a homebrew version of your current race to make the changes. 

Specifically, I think it best fits an example of a boon.

There is a system planned to support supernatural gifts, go now making them as feats is probably the easiest way.

It would basically have a variant race for every race as it does not stipulate human only, also remember it has bad drawbacks as it states the character registers as undead to spells so no healing magic and they can be turned unless they have one of the magic items that prevent turning.

Quote from Jacqsynn >>

It would basically have a variant race for every race as it does not stipulate human only, also remember it has bad drawbacks as it states the character registers as undead to spells so no healing magic and they can be turned unless they have one of the magic items that prevent turning.

 You can be healed and you wont be turned. You only register as undead to detection spells and effects.

Also, it isn't a variant race, it is a supernatural gift like a boon.

Quote from Jacqsynn >>

It would basically have a variant race for every race as it does not stipulate human only, also remember it has bad drawbacks as it states the character registers as undead to spells so no healing magic and they can be turned unless they have one of the magic items that prevent turning.

The body is alive, but the soul is missing (hence Hollow). You ping as undead to spells, while also retaining your original creature type (Fey if you're a Hollow Centaur, for example). Nowhere does it say you are turned by Turn Undead or unable to be healed.

I wonder how you would go about roleplaying one.

Just like a normal character?

A husk without any emotion or hope?

Filled with hatred and rage at your death?

Trying to pretend you are still normal but you always act a little off because you can't empathize with the living anymore?

I guess the latter one would be the most interesting but also the hardest to pull off.

Quote from Naresea >>

I wonder how you would go about roleplaying one.

Just like a normal character?

A husk without any emotion or hope?

Filled with hatred and rage at your death?

Trying to pretend you are still normal but you always act a little off because you can't empathize with the living anymore?

I guess the latter one would be the most interesting but also the hardest to pull off.

 https://www.dndbeyond.com/sources/egtw/character-options#HollowOne

The transition from life to becoming a Hollow One affects different people to different degrees. Some let their anger and regret consume them. Others use their second chance to become a brighter force in the world. However, all Hollow Ones are marked by their new existence: feelings of unease, dread or sadness cling to them like tattered rags of their past life.

As found in the Hollow One section of the book its seems like there are a few roleplaying elements suggested to the transition from living to "hollow".

The option seems a bit "meh" to me.  I mean it allows for a certain type of character but basically seems to strive to NOT give any real advantages or disadvantages for being a Hollow One.  I would like to like the option, just seems too shallow...