I use Adventurer’s Codex. It only works for 5e, and you have to enter and maintain things manually, but it’s really flexible because of that. It’s a web app, but it works pretty well on phones or computers and it’s FOSS.
If you need stuff to reference and help fill it in, I recommend either 5e.tools or dnd5e.wikidot.com. Both of those sites have all the released content for 5e in a well-organized format. I prefer 5e.tools for spells and the wikidot for… basically everything else.