"should carry over to Form 8606, Line 6."

8606-T and 8606-S, never combined on the one 8606.

"I have same problem with 2022 Lacerte."

The total is Per Owner. MFJ does not mean you combine their IRA account values. "all your traditional, SEP, and SIMPLE IRAs as of December 31, 2022" means, aggregating these account types, for purposes of figuring basis, % taxable, etc, for this one owner (who might have any number of these various plan accounts).

As for the rest, are you trying to enter that a Backdoor Roth of $6k happened in 2022? If so, did this person have no other amounts in any of these account types?

Backdoor only works as nontaxable when this contribution was made as nondeductible and nearly immediately converted and there are no other amounts in Trad IRS, SEP or SIMPLE; or, only Basis in any of these other account types.