Yes, the M134 7.62mm minigun can be handheld, but the recoil will most likely throw the user’s balance and aim off.
I read that it can be handheld in the Jane’s weapons hardcover books back in the 1990s at my college library. Those books cost several hundred U.S. dollars each. The M134 entry had a photo of the man-portable version with backpack. The backpack contains two cassettes of linked ammo although I don’t remember how many rounds the backpack contains.
On the other hand, the 5.56mm XM556 microgun is a better choice for man-portable minigun firepower.
The XM556 has been shown at AUSA and Defense expos mounted on the side of MRZRs and SOF unarmored and open vehicles. In an emergency or vehicle evacuation, the XM556 can be dismounted from the side of the SOF vehicle and carried with the Operator although I have not seen the ammo backpack designed for it.
https://www.emptyshell.us/xm556-microgun
I have not seen any SOF use either miniguns in a man-portable configuration in real life.