Aosp calendar is showing date 1970 and the google calendar is crashin every time I open it.
Try flashing and using OctOS, I have used that 3 months solid before with minor issues. (Just slight flickering from time to time).
I've looked back on these previous comments and it looks like an update to LOS's sources which has fked it up...
Try install a December - March build between 2017/8. (If you can't find one, if not let me know I may have one lying around on my PC as I previously owned this device. (I say this because I had OctOS running amazingly within this time.)
Forgot to mention that the security patch will be out of date but just don't install anything from dodgy sites and when you sideload, make sure it has an icon and the correct package name if you're unsure lmao.
I'm yet to see a virus affect Android if I'm honest...
If you have NFC I wouldn't recommend GPay if you do and can use it.