(Some of these may have the tiiiiniest bit of romance, but nothing super significant or that takes away from the story/characters as far as I remember) (Also, idk if you meant you wanted shounen, action, AND reincarnation in the same manhwa, or if those are just separate themes/genres you like. I based this list off the latter.)
The Dark Magician Transmigrates After 66666 Years
I’m Not That Kind of Talent
Eleceed
Trash of the Count's Family
Miss Guillotine
Polarity
The Boxer
Nowhere Boy
Weak Hero
Idol showbiz list.. Again skip tagged Romance..
https://www.mangago.zone/home/mangalist/2672591/
shounen, action, reincarnation/transmigration manhwas y'all like? May be it about dungeons, farming, cooking, idols, apocalypse, saving a novel/game character, saving the world etc.
Preferably no romance or harem. Thx in advance !