Marley's Monsters
Marley's Monsters is built on natural-fiber reusables: its UNpaper Towels are 100% cotton flannel (some lines organic), and the brand explicitly markets "no microplastics" as a selling point against the microfiber reusables it competes with. Cloths are sewn from cotton, so what sheds in the wash is plant fiber, not plastic. About as on-thesis as a cloth brand gets.
How clear are their specs?
States the cotton/flannel composition plainly and makes the no-microplastics point directly.