All hormonal and iud birth control methods do somewhat change the endometrium.

Regular combination bc pills cause slight thinning of the endometrium, this is what causes shorter and lighter periods.

Birth control is not an abortifacient. In clinic trials where women take the pill every single day at the exact same time, ovulation was prevented over 99% of the time.

Most women do not have 'perfect use' of the pill.

Diaphragms, the sponge, nfp/fam , and condoms, do not chnage the endometrium.

The copper iud floods the endometrium with copper, so that fertilized eggs may not implant.

What is your primary concern in looking for this specific type of bc method? May I ask?