I'm trying to install LineageOS on my Moto E4. I've been able to successfully sideload the custom ROM and boot into Lineage, but I can't install Gapps. Specifically, after sideloading LOS, I sideload the Gapps ROM. It gets to the message "Mounting partitions" and hangs there.
I don't know the precise reason why, but it was because I was booted into TWRP through fastboot instead of from a flashed recovery partition. After flashing recovery and booting there, the Gapps install completed without issue.