What are the device limitations for installing Linux-based Android alternatives?

I have a new Samsung Galaxy A40 and would like to use a Linux-based alternative to Android. Reasons: Privacy/security, hackability, moving away from Google. 1.) Can I install an alternative OS even though my device is not explicitly supported? If not, what are the limiting factors? Does each device require a specific set of drivers (e.g. graphics, audio, peripherals)? 2.) Are there any good OS options? Is anyone using Ubuntu Touch? The OS should be safe, stable and user-friendly. Also, using standard device functions and installing/sideloading APKs of standard apps (e.g. WhatsApp/Telegram/KakaoTalk) should be straightforward with no extensive workarounds required. PS.: I have no experience as a mobile developer.