For the moto E4, Motorola has a guide in their support site to unlock the bootloader. I used it to be able to flash a 64bit rom for my moto g4 plus and the process was pretty straightfoward, although you do need a pc to use the adb command line tool.
tomatoely
joined 1 month ago
Oh yeah. My initial plan was to install termux on it and use it as a server for a simple webpage I wanted to make, but the official rom i had was 32bit and the newer termux releases only support 64bit os.
I was going to give up, but while digging for more info I found out that for some reason the chip on my moto g4 was 64bit but not the OS. So I searched in the depths of the xda forums for a 64bit rom, which resulted in way too many dead links and dubious sources. Ended up using some obscure anime themed custom rom that crashed whenever I wanted to open the camera or use the flashlight BUT, it installed and ran termux nicely.
Overall I got what I wanted, but there wasn't any good quality rom I could find as they all had some sort of flaw. Hope you get better luck though! Those phones are still perfectly usable if not for lack of software support