atlas4409 UPDATE: When I woke up it was back in Russian. I have Russian installed as a system language (which I don't recall having installed), but English is set to highest priority so it shouldn't display Russian. Uninstalling the Russian system language obviously solved the issue, but this is still highly concerning.
You are probably experiencing the issue described in this thread: https://discuss.grapheneos.org/d/19518-grapheneos-randomly-changes-the-device-language
atlas4409 Bottom phone speakers stopped working.
Who knows what happened. Perhaps a hardware glitch? Did you get a crash notification? Without some form of log, trying to determine a cause would just involve lots of guesswork. If it doesn't happen again, I don't think there's any point in trying to analyze this.
atlas4409 I'm now trying to weigh the possibility of malware vs some sort of corrupt data.
Malware just doesn't behave like this. Why would an attacker risk making a compromise known by changing the system language?
atlas4409 I scanned for virus in settings and nothing showed up.
Not clear what you mean. GrapheneOS doesn't include any form of virus scanner. Do you mean the "Scan device" button in Settings → Security & privacy? That button does not scan for viruses or malware, it just checks for whether or not you have configured a screen lock. Perhaps it checks for some other settings as well but not much more.
atlas4409 I have issues with updating certain apps through Play Store and Aurora.
That sounds unrelated to the other issues. Would need a thorough problem description in order to help with this.