Yaarel
🇮🇱 🇺🇦 He-Mage
For others, the 2024 DMs Guide, page 55:They’re on page 55.
"Creating a unique background or customizing an existing one from the Players Handbook can reflect the particular theme of your campaign or elements of your world. You can also create a background to help a player craft the story they have in mind for their character."
5.5 intends for players to customize their background, but wants the DM to be able to use this design space to help contextualize the player characters within the details of the immersive world.
This approach encourages the DM to even create a new background feat for a truly custom character concept. While the DM becomes necessary, there is actually more customization possible in 5.5 than there was in 5.0.