No, Linux is not the issue -- my System76 Lemur holds 14+ hours. Haven't used X1 Carbon for a while, but it also held way longer than Framework.

How long does it keep its charge in sleep mode? Weeks or days?

	▲	heavyset_go an hour ago \| parent \| next [-]
		System76 edits firmware to enable S3 sleep on their machines. S3 sleep uses less power than Modern Standby.
	▲	rv3392 an hour ago \| parent \| prev [-]
		I believe they mean it lasts 14+ hours in sleep.