Does an Android phone without security patches cease to function?

OS security patches are less of a concern for older devices because the majority of the OS was still moved into Google Play Services and as long as the apps are still updated (eg, Chrome), the risk is very low.

Maybe I've been lucky here but my Oneplus One (April 2014), now flashed with lineageOS is still receiving updates.

Android version: 10.

Android security patch level: March 5 2021.

My 14 year old Motorola Razr doesn't receive any security patches.

Sad how gadgets become ever more brittle and unreliable as they get newer.

At least for me, I don't do banking on my phone and my main email is not tied to my phone.