Is there any way to make homebrew ores? If so, then where can i do it?

That depends on what you mean by “ores” and what you want to do with them.

Things like adamantite, mythril, etc. as well as combining different metals and rocks

You would just create Magic Items crafted from those metals. Keep in mind that Adamantine weapons are non-magic equipment, but adamantine armor and mithral armor are magic items that have been enchanted like any other magic item.

Well can you create custom ores like say netherite in D&D?

Quote from Hero6Pack >>

Well can you create custom ores like say netherite in D&D?

 
I don’t know what netherite is, but you can do anything you want in D&D. Who’s gonna stop you?

Netherite... is from Minecraft.

Do you know what Minecraft is?

I know of Minecraft but have never played it. It’s not my bag.

Quote from Hero6Pack >>

Is there any way to make homebrew ores? If so, then where can i do it?

 
Go to Collections > [Homebrew] Create Magic Items

Sidenote: Have you seen other people's creations?

• https://www.dndbeyond.com/magic-items/2362603-netherite-armor
  
  
• Here's a good example of an Ore entry
  https://www.dndbeyond.com/magic-items/3339391-pale-ore
  
  

If you still need help I can write one up for you, I take ***** or CashApp :)

Oh ok thank you