The Wanderer's Way

The Wanderer questline: claim the Vintage Probe on each of the seven planets, then greet the Wanderer itself. Each probe wants a Probe Scanner slotted into it permanently, so budget one scanner per probe - 7 Steel in all (Iron + Carbon + Argon each, so bring Argon along for Gas Giant while you're at it). Activate the scanner from a widget slot and follow the pings; a buggy makes each sweep painless (The First Discovery pops on your first).

The bit people miss: after you claim the final probe, a rift opens nearby and the Wanderer emerges. Go to it and interact - that is the unlock, so don't wander off before saying hello. If you do miss the moment, the encounter is repeatable with another Probe Scanner.