A creature who has been turned into an undead creature [...] can’t be raised by this spell.
The “has been” here is the “present perfect” tense in English, which can either indicate an action that was completed in the past, or an action from the past that is continuing into the present. That is, this line may be referring to creatures that were turned into undead and still are undead, rather than creatures that were at any point in the past turned into undead.
You could make the same argument for the clause I edited out of the quote, “or [has been] killed by a death effect spell.” If something was killed by a death effect spell, and then came back to life (was un-killed), and then died by some other means, can raise dead raise them? It’s unclear, because we don’t know if this clause refers to an action that occurred at any point in the past, or specifically an ongoing action that occurred in the past and whose effect still continues to the present.
Unfortunately, the ambiguity is impossible to resolve from the rules text alone. Resurrection and true resurrection give some hints, because they specify that they can raise someone who has been made into an undead creature and then destroyed (returned to simply “dead” status), but then that clause itself has problems because it contradicts other rules, which say those spells can directly raise someone while they are an undead creature. If a DM rules that resurrection and true resurrection can go directly from undeath to life, then they might also rule that an undead creature destroyed is just a regular dead body now, and can be the target of raise dead.
Barring that, though, to my knowledge resurrection and true resurrection are the only options. I mean, miracle or wish can probably do it, but if you can use those you can almost-certainly use resurrection.