Please recommend some good hiking courses in Seoul

‌
I'm a hiking beginner and I'm thinking of going hiking more often.
Since the world gets hazy with fine dust from November until next March,
I'm planning to go in September and October. Are there any good courses in Seoul?
Places I've been to:
Baegaksan
Inwangsan (I go here the most because it's close to home; the views are the best for the time spent hiking in Seoul, and the night view is great)
Ansan
Achasan, Yongmasan
Namsan
Cheonggyesan (It's a stairway hell, so I went once and vowed never to go again; you can't even see the scenery on the trail)
Gwanaksan (Sadang Ridge, Jauonam Ridge)
Bukhansan
(Sumeunbyeok, Baegundae, Baegun Information Center,
Bukhansanseong Information Center, Baegundae,
Bibong Ridge,
Uisang Ridge)
That's about it so far,
I haven't been to Suraksan, Buramsan, etc.