> so another package manager is needed for which grapheneos people seem to favor obtainium over f-droid, which I find is another strange decision

So just download f-droid yourself? Why the fixation on having a definitive, preloaded app store?

>I much prefer a fully OSS package manager and there is real value in having people compile from the sources externally, maybe even reproducibly so, instead of trusting the github packages.

Operating an app store is almost as much work as maintaining an Android fork, and it's hard to fault the authors for not sinking massive amounts of effort into doing it, when there's already f-droid, play store (plus aurora store), obtanium, and many others.