I notice when defining an start date on general ledger account the start balance is not computed correctly.
Can be reproduced on demo.tryton.org:

Fiscal year: 2020
Account: Main receivable
Start balance with no start date: 0€
Start balance with start date 1/10/2020: 0€ (should be 1924,45€)

Indeed neither general ledger line the balance with https://bugs.tryton.org/issue9791 works as expected when defining start date.