bcrypt is a good password hashing algorithm. It however needs some additional quirks for long passwords in PHP and should only be used if Argon2i is not available. bcrypt is not available on this system. TYPO3 password storage not only requires bcrypt itself, but also sha384 to be availble to use this algorithm. One of these or both are missing. bcrypt however can be used as a fallback if Argon2i is not available, too. Ask reach out to your hoster to fix both and prefer Argon2i.