ADB sideload regularly loads LineageOS ROM, but gets stuck at 0% with stock firmware, why?

I'm trying to restore the stock firmware for a Samsung S10e. It's currently setup with the LineageOS recovery image, and the LineageOS firmware. I've rebooted in the (LineageOS) recovery, factory reset everything, and now I'm trying to sideloading the factory image (G970foo_bar_baz.zip), however, it's stuck at 0%. If I try to sideload LineageOS again, it sideloads without any problem. Should I keep waiting? Since the factory ROM is very large (5.9GiB vs 800 MiB), it's possible that it's normal that it takes a long time before the sideload starts, however, I don't know how long should I wait.