Looking at Game Rules > Spells and choosing the "Noncore D&D" source category, I see the three spells of Lost Laboratory of Kwalish, but also two spells from XGTE: Summon Lesser Demon, Summon Greater demon.  On the other hand, Acquisitions Inc. spells are not currently considered "Noncore D&D" according to that list. I presumed they were when I asked my players to toggle off that option for our non Acq. Inc campaign.

In the magic items section, the "cap of water breathing" from the DMG is classified under Noncore D&D...

What classifies as "noncore" D&D when toggling on/off this source in the character builder?

"Noncore D&D" is a category WOTC ask DDB to add.  It mostly contains things that were created by WOTC for Extra Life fundraisers and have not been printed in physical books.  It includes things like the Lost Laboratory of Kwalish, One Grung Above, and the Tortle Package.  

I'm not sure why spells and magic items that are in Core books (like Xanathar's or the DMG) are showing up as non-core, unless they are provided in some of those non-core resources.

I can understanding thinking AI would count as Non-core, but it doesn't.  I do wish it were possible to turn it off as a source.

Continuing my search for "noncore" content on the site, I came to the same conclusion... I think items both in XGTE/DMG or other official source and on these non-core options wrongly type as "noncore", and that should be corrected.

As for Acq. Inc, I also maintain we should be able to turn it off. Adam (BadEye) said the team would stay attentive to feedback regarding this issue and report back to WotC. It's frustrating to feel "trapped" with Acq. Inc content for non-Acq. Inc campaigns after paying to unlock that sourcebook. Cool/silly options when you play AI, but sometimes, you just want to play with your players a more "serious" version of D&D...

Noncore should only include partnered content/ unofficial things. It should not include XGE or anything else.

I would love to cut off AI content though. I don't watch it, none of my groups watch it and we have no interest in it (nothing against the cast and crew of that show) so I want to be able to cut it off.

Hey Benz74M - are you able to link the full URL (not the shared one but the one you see when you are viewing it) of the character sheet where you are seeing different things display/not display when toggling Noncore D&D?

The content you are referring to should show no matter what, as spells from XGtE or the Cap of Water Breathing from the DMG cant be toggled off at all, as they are considered Core.

Sorce, in the first post, Benz74M specifies that this shows up in what we used to call the listings.  I can verify this.  If I follow their instructions and go to Game Rules>Magic Items and set the category filter for NonCore, the cap of water breathing appears.  If I do the same with spells, two summoning spells from Xanathar’s appear, in addition to the spells that are in the non core materials.  Now maybe all of those are reprinted in a non-core source, and that’s why they show up that way.  But I wasn’t able to find them in a non core source.