I was waiting for more lore to try and not contradict anything with my ideas, but I'll fling my idea out.
I'm thinking ex-corp, specialist researcher into manatech but progressively unable to overlook the human consequences of their research, so they turn saboteur, destroying the facility they work in and using the opportunity to be recorded as dead, drifting their way through various resistance groups, gaining more 'rough tech' skills until they make their way to LSS, where they feel there are sufficient resources available to be able to make a difference.
Wasn't too sure on the overall tech level generally, but I envisioned them as someone who utilised 'primitive' infrastructure like manual circuitbreakers, wired LAN networking separate from wireless grids etc. to try and minimise the potential for remote surveillance and sabotage of systems. Methodical and meticulous, a penchant for over-preparation that some might consider paranoia if they weren't so damn calm about all of it. That being said, they have a tendency to panic when all their contingencies are expended and they no longer have a plan on their hands because that degree of control is their coping mechanism of sorts. Outside of mission, not one for small talk - the sort of person who can just sit next to friends drinking at a bar and be content with just that, but has a tendency to speak up they deem it important/useful. A tinkerer with bootlegged scraps of tech and other useful bits and pieces, the kind who'd rather open stuff up and purpose build what they need rather than go out and acquire it. Definitely keen to get their hands on any usable manatech they can to repurpose it to useful ends.
Toying with the idea of them having a family from their corp life that also thinks they're dead which could provide some extra flavour/ammunition to be used against them once things go south and they potentially get exposed, as well as any other consequences of their past that could be thrown their way. If facial modification is available on the down low probably had some of that cheap if they could get it.
Sorry it's a bit rambling, will try to format for coherency at a later date.