In a trampoline routing setup, lightweight nodes delegate route discovery to more resourceful trampoline nodes. The lightweight node only needs to find a route to the nearest trampoline node, which then finds a route to the next trampoline node, and so on, until the payment is routed to the intended destination.

Any node on the LN could technically become a trampoline node. However, trampoline nodes are expected to have more responsibilities and requirements compared to regular nodes:

Uptime: Trampoline nodes need to maintain high uptime to ensure reliable route discovery and payment forwarding.

Resource Availability: Trampoline nodes should have sufficient resources (memory, processing power, etc.) to compute routes across the entire LN.

Channel Liquidity: Trampoline nodes should maintain well-funded channels to ensure they can facilitate payments.

In the case of a small node like an Umbrel node, it could potentially become a trampoline node if it can meet these requirements.

Trampoline routing involves trade-offs. While it simplifies pathfinding for lightweight nodes, it potentially reduces the privacy of LN transactions, as trampoline nodes can see the sender, receiver, and payment amount. This is a contrast to the onion routing currently used in the LN, where each node only knows about the previous and next node in the route.