Switching to rolling (testing) release

Hello FreedomBox community!

I have three follow-up questions:

(1) When manually running updates (via ssh),

$ sudo apt update && sudo apt upgrade

I get the following message:

[…]
E: The repository ‘tor+http://security.debian.org/debian-security testing/updates Release’ no longer has a Release file.
N: Updating from such a repository can’t be done securely, and is therefore disabled by default.
[…]

Is not having a Release file for debian-security an issue? If yes, can you provide some instructions for how to fix it? If not, can I safely ignore the message?

(2) I noticed that buster-backports was enabled in /etc/apt/sources.list.d/freedombox2.list, and since I want to have a rolling release I have commented it out.

$ sudo nano /etc/apt/sources.list.d/freedombox2.list

# This file is managed by FreedomBox, do not edit.
# Allow carefully selected updates to ‘freedombox’ from backports.

#deb tor+http://deb.debian.org/debian buster-backports main
#deb-src tor+http://deb.debian.org/debian buster-backports main

Is this correct?

(3) Now that Buster has moved to stable, when can users expect that Plinth will update beyond v. 19.2?

Thank you!
DJ