Yes I have a similar experience. In the early days of LOS 20 on the FP4 I got 10+ days of standby usage with a fully charged battery (no Wifi/mobile/bluetooth connection, only 4G voice service, dual SIM).
From one day to another (and since then) I only get max. 2 days of standby usage, even without using the phone at all. No apps or settings were changed AFAIR, and the battery usage screen does not show any apps (the “highest” usage comes from “Mobile network”, but only 2%)
The only bug report I found last time I checked (2 months ago) regarding high battery usage was this one: