The above two had similar implementation and they were trying to use list of list of object like List<List<Leads>> to pass list of records can you try it once.
Let me know if it helps you and close your query by marking it as solved so that it can help others in the future.
>> https://salesforce.stackexchange.com/questions/196866/passing-a-list-of-records-to-an-invocable-method
>> https://developer.salesforce.com/forums/?id=906F00000005GQdIAM
The above two had similar implementation and they were trying to use list of list of object like List<List<Leads>> to pass list of records can you try it once.
Let me know if it helps you and close your query by marking it as solved so that it can help others in the future.
Thanks.