How to check off records on a list view and pass them all to a Flow (button)

Submit multiple records to a flow: https://bigassforce.com/flow-list-buttons

Within the flow, 'Get' the records with ids in the collection variable: https://unofficialsf.com/easy-in-filters-in-flow-with-the-filter-query-flow-action/

I have not used this but @Hz says it works.