Here are three gei-comi that I recommend for BL audience, through which they can get an insight into non-BL queer manga from Japan (created with androphilic men as target audience) :
Fire Code by Ichikawa Kazuhide
Fisherman's Lodge by Gengoroh Tagame
Coming Home by Go Fujimoto
Here is my BL versus gei-comi list which I think highlights their differences and similarities (I have included only Gengoroh Tagame’s works since they are probably the easiest to access/buy/borrow):
Do You Remember South Island P.O.W. Camp? by Gengoroh Tagame || Hitori de Yoru wa Koerarenai by Matsumoto Yoh
Arena by Gengoroh Tagame || Jinx by Mingwa (Korean; detailed pitch here)
Cretian Cow by Gengoroh Tagame || The Orc Bride by Madobuchiya (Nishin)
Uo to Mizu by Gengoroh Tagame || Terpenoid by Okadaya Tetuzoh
My Brother's Husband by Gengoroh Tagame* || The Story of My Brother by Ike Reibun
There is overlap between BL and gei-comi. Gengoroh Tagame first published in JUNE. There are magazines and anthologies (Nikutaiha BL) that offer crossover between BL and gei-comi.
[* - aimed at non-specific seinen audience like What Did You Eat Yesterday]