The instruction list is current and comprehensive, but full attention should be given to the additional software list otherwise the installation will fail. Recommend a full binary install with cmake -DCMAKE etc about the third paragraph. Don't forget to adduser svxlink. Probably difficult to find a pi b+ these days, but pi 2 or 3 are good, even a banana pi or orange pi are similar but I have no experience of those. On some installations I found using sudo preceding all commands prevents permissions errors in the build , but not supposed to be the case.
Chris f5vmr g4nab