https://www.mangago.me/read-manga/butler_nabit/
https://www.mangago.me/read-manga/love_is_an_illusion/
(Although this isn't beta into omega but uke thinks he's an alpha)
(●￣(ｴ)￣●)
https://www.mangago.me/read-manga/kami_sama_wa_chotto_dake_ijiwaru/
https://www.mangago.me/read-manga/kyou_kara_omega_ni_narimashita/
https://www.mangago.me/read-manga/boku_no_omega_yo_samenaide/
https://www.mangago.me/read-manga/my_sweet_and_bitter_mate/
https://www.mangago.me/read-manga/omega_bus_stop/
https://www.mangago.me/read-manga/romance_but_not_romantic/
https://www.mangago.me/read-manga/stigma_2/
https://www.mangago.me/read-manga/raising_beta_winnow/
https://www.mangago.me/read-manga/gunjou_other_half/
https://www.mangago.me/read-manga/willow_love_story/
https://www.mangago.me/read-manga/kimi_wa_beta_pcbs/
wow that's a lot ! thank you!
recommend some story where the mc, beta suddenly turns into an omega (with smut)