Unofficial Factorio 2.1 fix of Orbital Transfer. Original mod by Urthen; 2.1 fix by kfsone.

Adds Orbital Transfer Provider and Requester chests. Platforms orbiting the same space location can exchange items:
a Requester with a filter set pulls a full stack from a Provider holding a full stack of that item and quality on another platform
(same force). Only one stack at a time; a Requester only accepts a new stack when empty.

This mod replaces the original Orbital Transfer and is flagged incompatible with it: disable or remove the original first.
Prototype, recipe, technology and setting names are unchanged, so your placed chests, research and settings carry over.
The original keeps its bookkeeping in script state tied to the mod name, so on first load in an existing save this mod
re-registers every chest on every space platform from the placed entities. Deliveries that are in flight at the moment you switch are lost
(one stack per delivery, ~1 second flight at default settings): let transfers land before swapping, or accept the loss.

Changes versus the original: Factorio 2.1 compatibility (logistic container animation/robot_door, default_empty_slots_signal),
the rename, and the state rebuild.
Source and issues: https://github.com/kfsone/orbital-transfer