⟨09drveyl⟩ Not as much as we'd hope.
Iirc iridium does it.
Starlink it is planned and satellites have the hardware but I don't think it's active yet or maybe that's a recent development.
TDRSS was designed for it.
Most of the time you just don't need the inter satellite relay around earth. It's almost always easier to add another ground station, especially if the orbit is higher.
For distant planets, you're talking to the DSN. You mostly just accept losing comms temporarily, so you don't have a thorough network.