Scrotum, because it's only a skin fold like other parts of skin and also it is good supplied with blood.
I have test it and it's no difference between IM, subcutane belly and subcutane scrotal. Butr also here, you need the right product and still have found only one what is perfect with no bubble building, hurting and haematome.
Also for IM usage, if it is hurting days after injection in German: Injektionskater), it's not your failure, this is the oil base of the injectet product which isn't optimal for you.
Why should DHT higher if you don't inject intra muscular? Also the bodypart has no consequences on converting to DHT, E2, what ever.
It doesn't matter where you inject.

The only difference is, how fast the testo is absorbed into the bloodstream. Subcutane the rate is a bit lower but more seadily, what is perfect for TRT, but not so the whish of peoples in Cycles.
I'm only doing subcutane. It's senseless and much more dangerous to hit your muscles with needles.
Ah, I forget... the reason to try scrotal was because subcutane injection leaves ugly blue areas on skin. On the scrotum it would be no problem. Nobody would see it. But, like I wrote above, with the right enanthate I have never had blue areas after injection. So the belly is ok, but scrotum is also possible.