In CPython, when a task awaiting asyncio.gather is cancelled, gather gets cancelled, and then all tasks gather is awaiting are cancelled. In MicroPython v1.17, it seems only the first gather task gets cancelled:

import uasyncio as asyncio
task = None
async def test1(r):
    while True:
        print(f"Test1 {r}")
        await asyncio.sleep(1)
        
async def test2(r):
    while True:
        print(f"Test2 {r}")
        await asyncio.sleep(1.65)

async def cancel():
    await asyncio.sleep(10)
    task.cancel()

async def main(r):
    await asyncio.gather(test1(r), test2(r), cancel())

async def run():
    global task
    for i in range(10):
        task = asyncio.create_task(main(i))
        try:
            await task
        except BaseException as e:
            print(f"Caught exception {e}")
            pass

asyncio.run(run())

Note that test2 tasks keep accumulating, whereas test1 gets cancelled correctly. Interestingly, these uncancelled tasks stay in the event loop even after run() completes normally, so that future runs include the "zombie" test2's.

Both of these behavior differ from CPython (v3.9.7).