Bookkeeping core
QuickBooks
The captured pages are a privacy statement, and I found no public information on the ledger underneath the product — nothing on double-entry, SKR03/SKR04 charts, journals, opening balances or a period close. A product name in an accounting category is not evidence of a posting engine, so this sits at the lowest step.
Xero
The evidence evidences invoicing, bill entry, bank reconciliation and reports — the pretty screens — but not one word about double-entry, a chart of accounts, a journal, opening balances or a period close. No SKR03/SKR04 anywhere, so as evidenced there is no German ledger underneath at all.