I’ve always used ColorNote. It does have several advanced features but they’re all optional. It’s been updated for 5 years now and basically hasn’t changed. Still free, no ads, easy to use. A rare exception on the Play Store. Whole app only 4Mb.

Do owners actually want thin? I’ve never heard anyone brag about how thin their phone is. I’m almost positive the thin fetish only exists so companies have a nice easy number to advertise, like all the useless numbers they slap on processors and TVs.