5500-SF vs 5500-EZ eligibility

if a plan currently has provisions for non family participants, and has had non family participants in the past, but currently only the owner is participating, however the plan still allows for non family participants, would one file the 5500-SF or the 5500-EZ for 2022? 

Sounds like it'll depend on how long ago the last non-owner participant still had a benefit in the plan.

Several years ago which would make one think the 5500-EZ form but the 5500-EZ form can not be filed unless plan characteristic 3E is present, which states

"A one-participant plan that satisfies minimum coverage requirements of section 410(b) only when combined with another plan of the employer"

does a plan that allows unlimited participants contain this characteristic, merely because their is only 1 owner participant this year?  That's what's giving me pause on the 5500-EZ form

That doesn't sound right.  The 3E code is specifically for a situation where the sponsor has two plans, one for himself and one for his employees but has to test them together.  (That way, the employees' Summary Annual Reports don't reveal the owner's riches, like if a small plan has 3 million dollars in it and the staff people are low in quantity and experience, and realize the only way their plan has that much money in it is if it's all the boss's.)

You can use an EZ without needing the 3E code, and if this guy hasn't had employees in years, the 3E code wouldn't apply since there's no coverage test issue.