For isekai...I recall the protag from https://mangadex.org/title/b4615bd9...yajin-tensei-karate-survivor-in-another-world grows a manly beard, but it's been a while since I read it so I don't know if he keeps it. I have a vague notion some of the other ossan/ojisan isekai/lite fantasy may have moustaches, but not full glorious soup catchers, alas
I like proper ojisans too.
There's I'm Still Alive
Many works by Fukumoto feature various kinds of old men, check out Strongest Man Kurosawa
For younger, but still beardy ojisans I know: Summit of the gods Saltiness
And you probably know vagabond, which is confirmed to never ever be completely finished.
Many samurai Gekiga-type Manga have glorious Toshiro Mifune beards on their dudes.
And there's also this, which is not what you asked for but hey he has a beard.