They need to use doppelgänger blood for the spell but yeah she and hope defiantly could

Any witch can cast a vampire spell. If a witch knows the spell and has access to doppleganger blood then they can cast it. The ingredients to create a vampire is the sun, white oak, doppleganger blood and dark magic. Being a Mikaelon isn't important to casting the spell.

not quite, apparently the vampire would not trigger a bloodline like the Mikaelsons, nor would it be able to create other vampires, Esther linked the six original vampires who were able to generate others and also trigger their bloodlines, in addition to the fact that the spell was only in the possession of Esther who created it and in her book that only Mikaelsons have access to it, probably only Freya or Rebekah and Kol possessing witches would be able to perform this spell if it was that easy Trinity and Strix already would have gotten rid of the Mikaelsons a long time ago, plus the fact that vampires created after the originals Alaric and Marcel need to have their backstories much deeper about generating bloodlines, apparently Lucien and Marcel can only create other vampires, they don't have a bloodline defined still in the series and with the end of Legacies we will never know.

@KnocknickKnock they'd need the blood of a Mikaelson witch to do the spell. Vincent performed it in The Originals and he needed Freya's blood. Not quite sure about the doppleganger blood.

@Sorrow Blue

That was for the Beast spell because they were turning an exisiting vampire into something new. It wasn't a requirement for the vampire spell that Esther used though. Her blood was not one of the ingredients in her spell. The Beast spell and the Vampire spell are two different spells.

Also yes you don't need doppleganger blood for a species spell as many have done without it. So you 100% can create a variation of Esther spell without Doppleganger blood. However to cast the specific spell Esther used to create vampires you would need doppleganger blood.

it needed blood from a Doppelganger or a more powerful creature for sure, you're forgetting that it was an immortality spell? to perform a spell like that needs a very large amount of magic it's not just any witch who performs it, it wasn't a spell to create werewolves if that's what you want to explain, even why the Hollow used death itself as a source of energy, which was strong enough to create the werewolves, the variation of Freya's blood or Tatia's blood was why it needed of a large amount of magic to perform the vampire creation spell, because every immortality spell needs a massive amount of magic to be able to be performed, Qetsyah used her blood or raw power anyway her magic was great enough for such a feat, if I'm not mistaken, they already said that drops of her blood were enough, Esther used the blood of Tatia and Lucien with the help of the ancestors and Vincent to cast the spell apparently used He had the blood of Freya's Firstborn, so it was said that Lucien knew about Dahlia, and surely he must have known the amount of magical power a Mikaelson Firstborn had.

and yes before they say that it is not the only alternative, it really is not the only alternative to use the blood of a Doppelganger, but there was no powerfully immortal being to have his death channeled into the spell, or even another supernatural being with enough magic to do so. used in the ritual, not even a Doppelganger since they didn't know about Elena or that she had taken the cure so she could use her blood again.

Lucien didn't use Freya blood to power the spell he used the Ancestors this was made clear by Lucien, Vincent and Freya. Especially Freya and Vincent who couldn't undo the spell because it wasn't her nor Vincent magic that cast it nor did she have enough power and needed the Ancestors.

You are all the time creating a pretext to say things that don't make sense, first you said that any witch can create a vampire and to create a vampire the witch needs extra magic to feed immortality, and you even compared it with creations of other beings (werewolves the only one so far) since it's not the same thing, so you said the doppelganger blood wasn't necessary, it was used to create vampires and the hybrid curse was obviously necessary, now you said it was the ancestors who cast the spell ? they just forged the poisons so that Klaus' blood wouldn't be able to heal the bite, and they even used Vincentt because they needed to prevent another witch from breaking the spell, and it would only be possible with the magic of the ancestors, which Freya didn't have access to because she wasn't a New Orleans witch, that's why they used Vincentt who even became the regent, he who cast the spell, which you yourself said wasn't him, the ancestors just used their influence to make sure the plan worked by delaying Klaus and Elijah and ensuring they could eliminate Mikaelson.