Fair Value Measurements - Schedule of change in the derivative liability forward purchase agreement (Q3) (Details) - USD ($)		3 Months Ended
Mar. 31, 2021	Sep. 30, 2021	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Derivative liability opening balance	$ 11,655,000	$ 12,321,000	$ 11,655,000
Change in fair value of derivative liability - forward purchase agreement		(3,330,000)	666,000
Derivative liability ending balance	$ 11,655,000	$ 8,991,000	$ 12,321,000

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=117331979&loc=d3e41228-113958

Name:	us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant