In 21.3 and later the first non-self argument is no longer a Request, it's the path, so this looks a bit confusing.
Since request is not being used, is there a reason to not just write it as follows?

def sentry_router_get(self, *args):
    # type: (Router, *Any) -> Any
    rv = old_router_get(self, *args)
    hub = Hub.current
    ...

it was burdensome to modify the code that worked fine.

I have reduced the changes as much as possible and only changed the changes for 21.3.

Hey @untitaker or @ahmedetefy, what's needed for this PR to make it in? Hopefully you are the right people to ask.
We are currently stuck on an ageing version of Sanic and can't upgrade without this

We will handle it this week

Hey @cakemanny did you manage to run the tests for sanic > 21.0?
I have tried running tests for version 21.3 and they seem to be broken

Hey @ahmedetefy, well, I have now 😅 . Looks like they broke when going from 20.9.x to 20.12.x :(

This is what you were seeing, yes?

_____________________________________________________________________ ERROR at setup of test_errors ______________________________________________________________________
tests/integrations/sanic/test_sanic.py:19: in app
    app = Sanic(__name__)
venv/lib/python3.7/site-packages/sanic/app.py:97: in __init__
    self.__class__.register_app(self)
venv/lib/python3.7/site-packages/sanic/app.py:1444: in register_app
    raise SanicException(f'Sanic app name "{name}" already in use.')
E   sanic.exceptions.SanicException: Sanic app name "tests.integrations.sanic.test_sanic" already in use.
...

Basically it looks like they've added a check to stop people accidentally re-declaring the same app.
I'll try to have a look into this but I'm shortly about to go on holiday for a week and a half. So if anyone else reading this wants to look in the meantime, feel free.

No need, I have already picked this up.. will push a PR soon