How to create Custom Advancement Triggers(1.19)

As the title reads, I've been trying to create a custom advancement trigger to activate based off a capability I've created. Despite my best efforts to A)Understand the sparse documentation for 1.19 on advancements and B) Reverse Engineer it by looking at the code, I keep coming back to this spot stumped. If anyone has example code using the SimpleTriggerInstance/AbstractTriggerInstance then I would be set and done. If you could explain what this line of the documentation is asking me to do, "Custom criteria triggers can be created by implementing SimpleCriterionTrigger for the created AbstractCriterionTriggerInstance subclass." then that would also be amazing. I've tried implementing it but it doesn't seem to actually want to be implemented, and extending it leads me in a direction that the documentation doesn't explain.