Will Debian 10 official "just work" on Librem 14?

That completely depends. As a maintainer of packages in Debian, I have seen bugs in those packages in a downstream distros LTS version. (Not PureOS in this case, just to make things clear), which I have tried to fix in this downstream. Providing a fix, uploading the package to the proper place, marking it as fixing the bug and ready for testing, doing all things to get the fix included. And nothing happens. The bugs are there because the distro simply takes a snapshot of Debian at an arbitrary time with development packages not ready for release, and makes a release of this. This experience have made me ignore bugs in that distribution completely. One reason for this might be that very few people use the specific package (on that distro). But I think that should be beside the point. If a fix is there and someone has done the work needed, it should be included.

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