The SRD is issued under the OGL and the first 2 pages of the SRD are the OGL.
If you choose to use the OGL (and you have to for a homebrew setting), you can only use content from the SRD. The only Cleric domain in the SRD is the Life domain so that is the only published one that you can use or make reference to. Similarly, you can only use magic items, monsters etc. that are in the SRD.
If you want to use all of the published D&D 5e material, you can use Dungeon Masters Guild but you must have no setting or use the Forgotten Realms, Ravenloft, Eberron or Ravnica settings. This doesn't seem like it would meet your needs.
Where is this limitation?
- Use of Product Identity: You agree not to Use any Product Identity, including as an indication as to compatibility, …
There is a list of things that are unambiguously Product Identity in the 4th paragraph which includes “Player’s Handbook” and “proper names (including those used in the names of spells or items)” - cleric domains are in the Player’s Handbook and reference spells (making a reference to them indirectly a reference to those spells).
However, the explicit list doesn’t exhaustively define Product Identity. Product Identity is defined in 1(e) and includes “characters”, “thematic elements”, “designs”, “concepts”, “themes”, “names and descriptions of … special abilities” and “magical or supernatural abilities or effects”. The clause goes on to state that Trademarks must be identified as Product Identity but cleric domains are not trademarks.
The definition of product identity is extremely broad - so broad that it will likely capture everything WotC (or TSR) have ever written.
An argument that cleric domains are not captured is doomed to failure.
But surely, I can just refer to this stuff?
In general, yes. Reference to a copyrighted work does not violate copyright and even copying parts of it for private use (as in your home campaign) or for commentary and education (as on this site) has fair use/dealing protection.
However, using WotC copyrighted work to make a derivative work (your campaign world) to sell is not fair use/dealing. You are only allowed to do that in accordance with the terms of the licence issued by the copyright holder, WotC. And they say, you can't refer to anything outside the SRD in your derivative work.
It's not that the reference is copyright violation - it's a violation of your contract which means you don't get the benefit of the licence which makes the rest of your derivative work copyright violation.