For everyone unaware, enabling developer options already makes your OS less secure, so Google is requiring you to make yourself more vulnerable just to have the right to install any software, not just those allowed by Google. This has been among others confirmed by GrapheneOS themselves:
It's developed by singular person as you read in their FAQ: "Donut Browser is built by one person with the goal of making the internet a little more private. Paid plans are how commercial users support the project and keep it sustainable."
Which is concerning.
It also promotes illegal practices as it can be seen here: https://donutbrowser.com/use-cases/automation/
I wouldn't recommend it.
Depends on your provider.
Personal attacks are used by people who lack valid arguments; therefore, I will block you to protect my psychological well-being.
Anyone interested in discussing actual Signal flaws, like the unecessary phone number requirement is free to reply and do so.
I read the article in the past, and it is still as flawed as it used to be. You're quite extremist without much legitimate reason. Signal is and will likely stay for the foreseeable time one of the most secure and private messengers.
https://keepandroidopen.org/