Unbound Merino
A performance/travel brand, not a plastic-free one - but a useful natural-fiber alternative to fully synthetic moisture-wicking underwear. Merino is the star and gives real odor resistance, but the boxer briefs carry a meaningful share of nylon and elastane (roughly 15%+ combined, varying by batch and color) for durability, so they rate minimal-contact. Buy for the merino odor performance, not as a zero-plastic choice.
How clear are their specs?
Lists a merino blend, but the exact nylon/elastane/TENCEL percentages vary by variant and aren't always consistent across listings - verify on the specific product before relying on a number.