

Cassian was there with the empire. Remember it was a penal unit, he was jailed for attacking a trooper with a stick, spent time in prison, got sent as a penal battalion according to him though Luthen says he was a unit cook. He was 100% on the side of the Empire as prison labor. The Mimbanese had been Republic aligned and trained by clones, but fought against the Empire sometime later. The scenes are too dark to make anything out, but the costumes for them have them using retrofitted or broken clone armor.
Read the YA book “rebel rising” which is about Jyn. It peters off, but the first half 2/3 is focused on her and Saw and is fucking fantastic. Pretty much letting Saw proselytize about how a rebellion requires violence and that people will only fight once the empire has created a pile of bodies so high it dwarfs them, and someone needs to create that be it dead imps those fighting back cause, or civilians the empire slaughters, but either way the rebellion will stand atop corpses. The latter half is weak teen romance, though then it picks back up with Jyn depressed in prison and waiting for death. That shit gets dark for a star wars novel