Mostly pretty positive actually, having some reasonable assurances that you’re actually running the software that you think you’re running seems like an obvious thing you would want.
Here’s an example of this in practice: https://grapheneos.org/features#auditor.
But I’m sure you know best. Time to cancel GrapheneOS.
Systemd is free software. The four essential freedoms necessitate that you have complete control forever.
The only way that you could lose control is if your hardware manufacturer took away the ability for you to install your own operating system. But then the choice isn’t going to be Windows or a Linux flavour personally blessed and tivoised by Lennart, it’s going to be Windows or a brick.