The NightOwl application has existed since 2018 and is used to automatically switch between light/dark modes on the operating system. It is an alternative to the built in macOS automatic mode which only switches when the user steps away from the computer.
However, the application has been bought out by “TPE.FYI LLC” in late 2022 that forcibly joins your devices into a botnet for use of market research, without your knowledge (other than the TOS in small text on the download page) or express consent (this feature cannot be turned off, even when the app is quit). This is documented in their terms of service.
Disclaimer : not an Apple user, not a lawyer
This should be illegal by European law. Without further knowledge it seems like a prime example for the GDPR letter of death and a pretty solid case for data protection lawyers
Unannounced changes to the Terms of Service are definitely illegal.
But various forms of backstabbing are legal as long as you let your users know that the TOS have changed. I mean, who reads that stuff anyway. You can literally throw in there whatever you like and people will just click “I agree” regardless.