I’m flying out of Eugene tomorrow at 9 am. What time should I arrive to get checked in and go through security?

I agree. TSA pre or not - security was 10 min max. If not checking a bag especially, then 15 minutes before boarding is plenty of time.

At least one hour

I would say a hour and a half early. If you are checking bags, give yourself a little extra time just in case that's slow. It is not a busy airport.

I flew out from Eugene to St George a couple of weeks ago and an hour was adequate for that airport. Though I must say it was flying out at 6 a.m. other times a day maybe different. I would think 9 a.m. would be a little busy but I was through there quite quickly and still had to wait a half hour before the flight left.

At the Eugene airport 2 hours is ridiculous I arrived an hour before my flight I was through TSA in 10 minutes. Maximum of an hour. Anything less than that I think would be stressful on me

I'd still give yourself 2 hours

An hour before boarding time is enough.