

The right answer is definitely not landfill.
Most people use their computers to run a web browser, maybe a word processor or media player, and… not much else. Even someone who has only used Windows can figure out those basics on a Linux desktop.
If the charities are unable/unwilling to provide support for Linux, they could give computers away on Craigslist before dumping more e-waste into our environment.
For anyone reading this who is unfamiliar with Debian’s release process, the Testing distribution is not a release. Rather, it is a holding area for packages that may eventually become part of a release.
Some people choose to run it instead of Debian Stable in order to get more recent non-security updates to packages, with the understanding that occasional breakage is normal for Testing.
https://wiki.debian.org/DebianUnstable#What_are_some_best_practices_for_testing.2Fsid_users.3F
https://wiki.debian.org/DebianTesting
https://www.debian.org/devel/testing