In Solo: A Star Wars Story, Solo enlists in the Empire with a career goal of being a pilot, but he washes out of the required training and is reassigned to infantry work.
During the period of Han's infantry service, Is he an Imperial Stormtrooper, or is he serving as some other type of infantry soldier? We know from the various movies that Stormtroopers typically wear the trademark white armor, though they (like most real life military forces) can and do wear different types of uniforms depending on the situation and climate. Does Han wear a brown/gray uniform with an open-face helmet due to conditions on the planet he finds himself deployed to, or is he simply not a Stormtrooper to begin with (and thus, not likely to ever wear the white armor)?
Considering Han's initial attempt at pilot training (part of the Imperial Navy), it stands to reason that it might have been administratively and practically easier to reassign him as an Imperial Navy Trooper than to transfer him to the Stormtrooper Corps, but this doesn't seem to be mentioned in the film.
The Imperial Navy Troopers ordinarily serve on board ships and space stations and I wouldn't expect them to be regularly deployed as ground/planetary infantry, but it is plausible that Solo and his team are on board a ship that crashes and are forced to "dig in" to the local terrain.