Regarding the OBS repo that is mentioned in this appendix:
It was last used for client 2.6.3 – and probably should have been removed long time ago. (Repo’s at OBS forget to refresh their GPG keys, when they don’t do rebuilds regularly, this is what now happened)
We have an update branch for the docs, but but no decision where and how to document client build instructions when that repo is gone. The instructions that we have compiled so far only work for reproducing exactly what we already have. It won’t currently help for Raspberry.