I use Nextcloud with Carnet. I haven’t used Keep in years so I don’t know the current features but when I made the switch to Carnet it was very comparable.
On Nextcloud it is an app you install separately. For your phone you’ll find Carner on f-droid. Sadly there is no client for iOS. Link https://www.getcarnet.app/
Thank you for that link and Thank you to Mozilla for doing those tests. I always suspected something like this but it is good to have it tested and in writing.
My only gripe with the article is this:
Renault and Dacia aren’t available in the US, so there is really no need for them to sign those principles. Which makes Tesla the only one where this is relevant.