Update: I found https://webhosting.coop/ and while it doesn't look like they host Nextcloud instances now, there's a chance they might be able to be convinced to do so in the future.
Discussion
Update 2:
I found a coop that will do this: mayfirst.coop
And one who will do this for non-commercial purposes: autistici.org
And if you're looking for just personal services, there's also 0xACAB.org