Would the 6th level Shepherd Druid’s Mighty Summoner feature works on summoned creatures not made from spells

To clarify, when I say "summoned creatures not made from spells", I mean summons that are from class features and the like, so the Shadow Sorcerer’s Hound of Ill Omen, the Hexblade’s Accursed Specter, Raven Queen’s Sentinel Raven (tho less hp on this would be nice) and the Beastmaster/Drakewarden’s Animal/Drake Companion. Sinces these are features that summon creatures, would they work with the Shepherd Druid’s Mighty Summoner if they aren’t technically spells?