I need thy help holy one!

Camping here..

Omniscient reader
The live
Lookism

Gonna need to watchover here too for sum recs like that ahe

https://www.mangago.me/read-manga/no_6/
https://www.mangago.me/read-manga/trash_of_the_count_s_family/
https://www.mangago.me/read-manga/trapped_in_a_webnovel_as_a_good_for_nothing/
https://www.mangago.me/read-manga/a_mild_noble_s_vacation_suggestion/
https://www.mangago.me/read-manga/saihate_no_paladin/

youve probably read a lot of these already, but if not, maybe check some of these out? (or basically: a list i crudely composed except the farther down you get, the farther i stray from the original assignment sorry this list is all over the place)

- fukigen na mononokean's bromance and adventure is elite. probably the only manga i can think of that perfectly fits your description tbh ( https://www.mangago.me/read-manga/fukigen_na_mononokean/)

- path of the shaman ( https://www.mangago.me/read-manga/path_of_the_shaman/).

- otherworldly sword king's survival records: the running gag of bl bromance between mc and his bud is so sTRONG (there are girls in the main cast, but if i remember correctly they have zero romantic interest in any guy mcs) ( https://www.mangago.me/read-manga/otherworldly_sword_king_s_survival_records/)

- trash of the count's family or omniscient reader's viewpoint (tho both don't rlly focus on bromance, more on just mc and his adventures)

- limit breaker maybe? idk if this is the genre youre looking for tbh bc it's less adventure and friendships, and more action, but mc shares a bromance (it's mostly backgrounded, though). all the girls have zero romantic interest in mc ( https://www.mangago.me/read-manga/limit_breaker/)

- the live. but mc technically has a (dead?) wife, and the guy he's with feels more like a younger brother you know ( https://www.mangago.me/read-manga/the_live/)

- dungeon reset ( https://www.mangago.me/read-manga/dungeon_reset/) lots of ppl ship mc with his old friend but the old friend only reunites with him WAY later in the story. idk if this story checks the bromance youre looking for but the plot is fun

- this manga,,,kind,,, of? at least there's a developing bromance between one of mc's specific enemies ( https://www.mangago.me/read-manga/seven_knights_alkaid/)

- this manga is literally the straight bl paradox. there isn't really one male companion like you're looking for, tho ( https://www.mangago.me/read-manga/isekai_tensei_ore_ga_otome_ge_de_kyuuseishu/)
- ^^ he is a highschool girl fits this too ( https://www.mangago.me/read-manga/he_is_a_high_school_girl/)

- bloody mary. it's intense action and less adventuring tho, and the queerbait is so fruity that the plot tastes like fermented caprisun. it should be illegal.( https://www.mangago.me/read-manga/bloody_mary_samamiya_akaza/)

- tokyo's revengers maybe? idk if it fits the vibes but it has the variables if u know what i mean. kinda like bloody mary
- ^^ same thing with apocalypse no toride and Yuukoku no Moriarty

Ohoooooo, thank you everyone, now imma enjoy my night (≧▽≦)

Just remembered so I'll add some more. These are by Sugiura Shiho and CLAMP. CLAMP often writes male characters with ambiguous bromance. Older Shounen ai mangas are usually great because they're plot heavy yet the MCs still have chemistry.

SH:
- https://www.mangago.me/read-manga/silver_diamond/
- https://www.mangago.me/read-manga/koori_no_mamono_no_monogatari/
- https://www.mangago.me/read-manga/shuuten_unknown/

CLAMP:
- https://www.mangago.me/read-manga/xxxholic/
- https://www.mangago.me/read-manga/gohou_drug/
- https://www.mangago.me/read-manga/wish/