1.) Place a Trial Spawner from the creative menu.

2.) Use a spawn egg to set the what mob spawns from the trial (husk is ideal for they can equip gear and don't burn in sunlight)

2.) Start and complete an ominous trial.

What happens is that mobs that should equip gear during an ominous trial won't and the loot from said trials will be the standard loot. HOWEVER, ominous effects like projectiles spawning will still occur during staged ominous trials.

What should happen is that mobs that normally have gear during ominous trials will have them and loot be from the ominous loot table.