How to disable autostart of an app on LineageOS 14? LineageOS used to have a function in the settings to activate and deactive the auto-start of apps inside Settings -> Apps if I recall correctly. I no longer find it in any setting option.

I'd like to avoid installing an extra app if there's a native function. The app in question is a RSS reader which I don't want to uninstall, but just not have running at every start.

I'm using LineageOS 14.1-20180203-NIGHTLY-titan.
Even since LineageOS was known as CyanogenMod, it offered a deeper way to manage apps' permissions than the one introduced by Google from Marshmallow onwards. This feature, known as Privacy Guard, can be accessed from within Settings -> Privacy.

To restrict it from starting on boot, hold on the target app in the list that's displayed, then find the Start at boot entry and flip its toggle. Even system apps can be restricted this way, provided you choose to display them via the menu located in the top right corner.

Note that this will prevent an app from firing up at boot, but that, if said app can receive push notifications and you use Google Services or microG, then it will be awakened to display the notification. microG offers a way to disable yet this mechanism.