Wish i knew more, but these are the ones i like
https://www.mangago.me/read-manga/ureoji_bl/
https://www.mangago.me/read-manga/kitto_oujisama_ga_nante/
https://www.mangago.me/read-manga/mitsuya_sensei_no_keikakuteki_na_edzuke/
https://www.mangago.me/read-manga/still_like_me/
https://www.mangago.me/read-manga/lovers_on_the_last_train/
https://www.mangago.me/read-manga/koi_ga_ochitara/ (vol 1)
https://www.mangago.me/read-manga/koi_ga_michitara/ (vol 2)
https://www.mangago.me/read-manga/on_doorstep/
https://www.mangago.me/read-manga/itooshiki_hibi/
https://www.mangago.me/read-manga/don_t_call_me_daddy/
https://www.mangago.me/read-manga/first_of_summers/
https://www.mangago.me/read-manga/old_fashioned_cupcake/
https://www.mangago.me/read-manga/midnight_rain_ctk/
https://www.mangago.me/read-manga/onsen_de_himitsu_no_otomari_241_kaime_naono_holics/
https://www.mangago.me/read-manga/the_monster_and_the_beast/
https://www.mangago.me/read-manga/joou_to_shitateya/
https://www.mangago.me/read-manga/sui_mo_amai_mo/
https://www.mangago.me/read-manga/mitsuya_sensei_no_keikakuteki_na_edzuke/
https://www.mangago.me/read-manga/can_i_hold_your_hand/ (one shot)
https://www.mangago.me/read-manga/oni_to_tengoku/
https://www.mangago.me/read-manga/tonari_ni/
https://www.mangago.me/read-manga/40_x_40_chikuwa_kaigi/
https://www.mangago.me/read-manga/jijii_no_koi/
https://www.mangago.me/read-manga/i_m_an_old_man_but_also_a_saint/
https://www.mangago.me/read-manga/confessions_of_a_35_year_old/
https://www.mangago.me/read-manga/it_can_t_be_mutual_love/
guys can you recommend some old man yaoi