Players can use the following sources to create characters
Core Rules (available online: Daggerheart SRD and/or Demiplane)
Demiplane includes a character creator that allows you to use the free version of the rules to create a set number of PCs. If you would like access to expanded options, contact Karen and she will send you a Demiplane source sharing link.
All official published material will be allowed
Official playtest material will be allowed, but keep in mind that mechanics may change during playtesting
Homebrew materials will be allowed, with permission from Karen
The Daggerheart site includes a section called The Void, which contains playtesting material
I am happy to work with anyone who would like to create a character using Eberron-specific content. For example: the artificer was created for Eberron but there is not yet an inventor-type class in Daggerheart; the Dragonmarked Houses are more like subsets of various races; and a sourcebook for 5e was recently released with playable monstrous races like medusas and gnolls.