The rule for initiative in PHB read (emphasis mine)
Initiative determines the order of turns during combat. When combat starts, every participant makes a Dexterity check to determine their place in the initiative order. The DM makes one roll for an entire group of identical creatures, so each member of the group acts at the same time.
I usually thought that identical creature stands for creatures of the same type and with the same name: for example, in a situation where a party is fighting 3 trolls and 2 ogres I read the above rule as rolling one d20 for the trolls’ group and one d20 for the ogres’.
Other DMs would extend identical to a wider meaning (see enkryptor’s answer to "Is this house-rule that has each monster/NPC roll initiative separately (even when there are multiple creatures of the same kind) game-breaking?"): for example, a dragon and their kobolds army fighting the party may be considered identical creatures in the sense that they are allies, as belonging to the same group of enemies.
Is there any RAW interpretation of the word identical in this context of initiative roll?