Rescue is at hand if you lost your inventory in Outriders... to a degree, anyway. Kotaku reports that People Can Fly and Square Enix have begun restoring equipment for "Group A" players who not only lost their gear, but couldn't login with one or more characters. You aren't guaranteed to get everything back if you were affected, unfortunately, but you should get all equipped items, all Legendary inventory items and all completed Accolades.
You'll only get 20 "previously acquired" non-Legendary items from your inventory, though, and they'll be prioritized based on rarity and the time you obtained them. If your inventory is full, you'll have to free up space before the server can provide your gear. Characters that can login may get as many as 20 "god-rolled" Legendary items they'd previously sold.
The restoration is still underway, so don't be surprised if you have to wait several hours or more as of this writing.
The developers haven't yet said when Group B players, those who lost items but could still sign in, will get their equipment back. Still, it's an important start — and it's good news at a time when many gamers can't take their progress for granted.