You don't have to lose it completely.

Use it to book a simple domestic one way to minimise Avios and taxes, then immediately cancel it for a Future Travel Voucher. This "wraps up" the 241 in the booking and keeps it valid until Sep 2023.

​​​​​​There are some limitations with this approach - you will need to phone up to use the FTV, it can't be booked online. Currently contacting BA by phone is...."challenging", but by the time you come to use it, things may be better.

Also, as I understand, you won't be able to change the names of the passengers.

With those caveats in place, it may still be with doing if you think you'll use it before Sep 2023.

(Edit: What Globaliser said basically! Too slow here...)