In the US, Bob’s Red Mill company sells whole flaxseed and hulled hempseed hearts. <-(don’t know if those count.)Chickens need a pasture with high biodiversity of flora and wild herbs and flowers that attract bugs to have benefits from free ranging.
Let them free range just a few hours in the afternoon and see if the situation improves.
For richer yolks try feeding them fresh chilies. For omega 3, feed them either whole flaxseeds or whole hemp seeds as treat.
Flax meal is a scam, omega3 will oxidize and be destroyed as soon as the seed is broken if not kept refrigerated and away from oxygen.
It’s sold widely in grocery stores, not just at Whole