Why are the new species not available to select from to build new Species Option? How do you create a Lineage for a 2024 race - like elves?

Because none of the new species get Species Options anymore. “Species Option” is what they’re calling what used to be “Subraces,” but those don’t exist anymore. Now those species have Options attached to specific traits or trait trees. You can learn all about how to set those up in the Homebrew Subclasses & Species FAQ, question #1: (https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/131411-a-homebrewers-how-to-faq#HomebrewSubclasses&SpeciesFAQ).

Then they need to add Create Lineages. Like the elf Lineages 'subraces'. You can't build a Lineage for a 2024 race. I want to create a Homebrew Elf Lineage.

You can, the Lineages are just Options attached to one of the Elf’s traits. They don’t make them like subraces anymore. Make a copy of the Elf and add ac4th Option to that trait.

I don't want to create a new Elf Race. Just as you used to create a new Subrace for the existing core race, for the new Species you should be able to make a Lineage so it gives you the proper spells, etc.

I don’t think you’re understanding what I’m saying, or I’m not understanding what you’re saying, or both. Bottom line is, from now on nothing like subraces will ever come forth out of WotC again for D&D. They’re not doing it anymore. That way of doing things got taken out back and put down, and will never be coming back again. There are currently only three lineages for the new 5e24 Elf species: Drow, High, and Wood, and the only mechanical difference between them is what you see in the Elven Lineage trait:

https://www.dndbeyond.com/sources/dnd/free-rules/character-origins#ElfTraits

Elven Lineage. You are part of a lineage that grants you supernatural abilities. Choose a lineage from the Elven Lineages table. You gain the level 1 benefit of that lineage.

When you reach character levels 3 and 5, you learn a higher-level spell, as shown on the table. You always have that spell prepared. You can cast it once without a spell slot, and you regain the ability to cast it in that way when you finish a Long Rest. You can also cast the spell using any spell slots you have of the appropriate level. Intelligence, Wisdom, or Charisma is your spellcasting ability for the spells you cast with this trait (choose the ability when you select the lineage)

It is not possible to just add an additional Option to that trait for the standard Elf species. There are only two ways to add any new Options to it:

1. Create a new Elf species using the original 5e24 Elf as a template, and then edit that trait to add your additional lineage Option.
2. Create a Variant for the 5e24 Elf and give it a trait that replaces the Elven Lineage trait.