If anyone's sperm goes inside the woman (except her husband) then this is haram. As touching, talking and even gazing any Na-Mehram is haram let alone putting sperms in her (by any means).
So, as to your question,"If two men could have a baby (e.g. via stem cells), would it be haram?". Yes, it would obviously Haram.
Mika'el is the name of an arch-angel.
من كان عدوا لله وملائكته ورسله وجبريل وميكال فإن الله عدو للكافرين
Whoever is an enemy to Allâh, His Angels, His Messengers, Jibrîl (Gabriel) and Mîkâ’îl (Michael), then verily, Allâh is an enemy to the disbelievers."
— Quran 2:98
اللهم رب جبرائيل وميكائيل وإسرافيل
O Allah, Lord of Jibraīl, Mīkaīl and Israfīl
The following are recommended acts regarding an infant in Islam:
Adhan. In the ear, note that this is generally considered recommended but is also disputed by some madhabs 1.
رأيت رسول الله صلى الله عليه وسلم أذن في أذن الحسن بن علي حين ولدته فاطمة
I saw the Messenger of Allah (ﷺ) say the Adhan in the ear of Al-Hasan bin 'Ali - when he was born to Fatimah
This hadith has certain issues that scholars have tried to address:
The hadith seems to say that only Mary and her child have been exempt from the touch of Satan which also may lead to the conclusion that 'Isa () and his mother () are of a higher rank than Muhammad (). This is one of the reasons why some scholars like az-Zamakhshari and other Mu'tazilah ...
There are two possibilities that can be noted.
All babies do eventually cry. It could be that eventual crying that is from the touch of Satan.
The hadith states that everyone except Maryam and Isa (AS) were touched by Satan. But, it doesn't require that everyone cried because of that touch. The touch could be the cause of the first crying in most babies, ...