I guess one thing I’ll point out: the “UUID” type used by the Tuple bindings is, I think, compatible with this spec (at least when the data are serialized). It encodes a 128 bit UUID as one (1) byte of type code followed by sixteen (16) bytes of data, and it isn’t particularly opinionated about what the data look like. This will then sort your UUIDs according to their unsigned lexicographic byte order, which I think is sufficient for this format. You might need some extra scaffolding to transform between UUIDs from the ULID spec and UUIDs that fell off a truck (or wherever), but I think it would do most of the low-level things, etc.
Uh, assuming that the spec is using unsigned 48-bit integers for the timestamp.
I think you’d need to be careful that ULID has a timestamp as a leading part, so inserting a series of ULIDs into a database would cause a rotating write hotspot, whereas inserting UUID v4/v5 would distribute over the keyspace well.