@forestine so I've been very happy with the Gilbert top by Helen's Closet. Though I don't do the tie version, just the short sleeves and the straight hem. It's darted so not what you're after but as plus size goes, pretty good, so possibly the dartless Cameron might work (
https://helensclosetpatterns.com/collections/tops/products/cameron-button-up) though not sure if it falls enough in women's patterns.
M&B waikerie is also dartless, I've made the 1 twice and wear it open normally