Loans and Borrowings - Schedule of Principal and Interest Payable Outstanding Amounts (Details) - EUR (€) € in Thousands	6 Months Ended
	Mar. 31, 2025	Sep. 30, 2024
Disclosure of detailed information about borrowings [line items]
Senior Note embedded derivative	€ 28,638	€ 28,638
Less: amortization under the effective interest method	(23,905)	(23,361)
Non-current liabilities	1,166,141	1,164,688
Current liabilities	€ 29,721	24,670
Term Loan \| EUR
Disclosure of detailed information about borrowings [line items]
Borrowings, maturity	2029
Non-current liabilities, gross	€ 375,000	375,000
Term Loan \| USD
Disclosure of detailed information about borrowings [line items]
Borrowings, maturity	2029
Non-current liabilities, gross	€ 154,336	152,883
Current liabilities	€ 7,964	7,890
Vendor Loan \| EUR
Disclosure of detailed information about borrowings [line items]
Borrowings, maturity	2029
Non-current liabilities, gross	€ 208,305	208,305
Senior Notes \| EUR
Disclosure of detailed information about borrowings [line items]
Borrowings, maturity	2029
Non-current liabilities, gross	€ 428,500	428,500
Term Loan interest payable
Disclosure of detailed information about borrowings [line items]
Non-current liabilities, gross	1,170,874	1,169,965
Term Loan interest payable \| EUR
Disclosure of detailed information about borrowings [line items]
Current liabilities	2,444	3,591
Term Loan interest payable \| USD
Disclosure of detailed information about borrowings [line items]
Current liabilities	1,585
Vendor Loan interest payable \| EUR
Disclosure of detailed information about borrowings [line items]
Current liabilities	8,355	3,816
Senior Notes interest payable \| EUR
Disclosure of detailed information about borrowings [line items]
Current liabilities	€ 9,373	€ 9,373