Sentinel does have Steel Skin at level 4, no? I don’t see where it says that you can’t pick a skill feat if it also has the archetype trait on it

Ah got it. Though I’m surprised about those archetypes you mention with no lvl4 feats. What are those?

I’m guessing those archetypes are simply not compatible with the rule?

You can still take a feat from your regular class at level 4, you don’t need to exclusively pick feats from your archetype once you have its dedication. I was wrong on that, I forgot that you get more free feats as you progress with your free archetype

There’s also nothing stopping you from picking any level 2 feat you’re eligible for at level 4, same goes for dedications. The feat level is really just a minimum level requirement.