One example of a useful technique
https://serenityos.org/ apparently only makes source code available. There are no binary images of the OS to install
I think Andreas said this functions like a little test -- if you're not willing to build it from source, then you might not be a good contributor. Or you might not be seriously interested in the project's goals.
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Likewise, my shell project provides source tarballs only, right now - https://www.oilshell.org/release/0.21.0/
It is packaged in a number of places, which I appreciate. That means some other people are willing to do some work.
And they provide good feedback.
I would like it to be more widely available, but yeah I definitely see that you need to "gate" peanut gallery feedback a bit, because it takes up a lot of time.
Of course, it's a tricky balance, because you also want feedback from casual users, to make the project better.