any ideas on making an android phone (LOS 22.2, root) more dormant in standby?

I got a couple older ex-flagships with beefier SoC that aren't super-energy efficient and chew through the battery without doing anything. they got no SIM cards and broadband is disabled by way of Airplane mode, they're on wifi with very few background apps (syncthing, KDE Connect - tried without them, same) and still they barely last 24 hours doing nothing, just sitting there with SoT of like 5 mins.

tried just LOS (with unifiedpush) and LOS + microG + replace FOSS apps with Gplay apps, thinking that background sync could be the issue, no significant difference.

I've tried some tools like 3c CPU Manager that let you underclock CPU and GPU, but them things are for people trying to maximize their SoT, like use less power while they're being used. what I'm looking for is something to bring the consumption way, way down when it's not being used.