Terrible battery life in sleep

E14 Gen 6, running ubuntu 25.10. Battery drains about 40% in 8h of having the lid closed. Apparently modern laptops don't support S3 sleep anymore and they have 'modern standby' instead which keeps some things awake?

I've done some searching and most posts relating to this issue say to change the BIOS sleep setting to Windows/Linux to enable S3 sleep but that setting doesn't exist in the current BIOS version.

Linux reports the only mem_sleep option is `s2idle` and not `deep`.

I have zero use for any modern/connected standby crap; when the lid is closed I want minimal power usage and nothing runnnig. How do I get this?

My old thinkpad t470 which had a battery life while being used of about 30 minutes could stay in sleep mode for a whole day no problem (and before the battery degraded so much, a lot longer), so this is pathetic performance from a much newer machine.