Two levels, and we name the screen each one came from
The signature algorithm is chosen per user, when the user is created, rather than fixed for the fleet. The create user dialog shows it in the signature algorithm field, where a device certificate is issued with ML-DSA-65.
The authority above it sits at another level. The per gateway rotation dialog reads Current CA algorithm: mldsa87, with a selector for the next rotation.
Two uses, two levels. We name the screen each one came from rather than rounding them into a single number that would be wrong on one of the two.
The same crypto agility runs The Vault, which offers eight certificate authority options, from RSA-2048 to ML-DSA-87, and re-signs and redistributes the certificates itself.