Inside that coroutine get the loop and await loop.sock_accept(sock)
And then asyncio.create_task(on_connection_data(connection)).
The only gotcha is you need to keep a reference to that task so it doesn't get garbage collected.
Consider organizing the code using TaskGroup.
"The default build implementation is a generational collector. The free-threaded build is non-generational; each collection scans the entire heap."
https://devguide.python.org/internals/garbage-collector/
https://docs.python.org/3/library/gc.html
(And as someone else pointed out, asyncio's event loop keeps only weak references to tasks, so the GC implementation doesn't really matter here.)