I have had a travel voucher, originally a non-refundable business class flight with Air Canada / Lufthansa, booked via Expedia.ca for April, 2020. Soon after the pandemic, I received an email from Expedia telling me that because of the flight cancellation by both Lufthansa and Air Canada, my booking was Converted as a travel voucher of $5770, with the expiry date of April 2021.
Today for the first time, I called Expedia.ca, and the answer was that this voucher credit has been extended for another year with the new expiry date as April 2022. Because Air Canada is the departure source airline, I am able to confirm it via Air Canada about this voucher as well. Assuming that Air Canada has cashed this full amount of money after my booking last year, and has not shared with Lufthansa. I was informed that I could reroute any future booking to any destination, as long as Air Canada/its codeshare partners fly.
this may not answer your question for all, since not sure all airlines will extend or have extended the vouchers from Expedia to another year. But hopefully you find out a good outcome.