How to install QGIS 2.99.x master on Raspbian GNU/Linux 8 (jessie)

Question

I want to install QGIS 2.99.x master on a Raspberry Pi 3, but there is something going wrong. First I've added the following lines to /etc/apt/sources.list:

deb     http://qgis.org/debian-nightly jessie main
deb-src http://qgis.org/debian-nightly jessie main

Unfortunately, this installs QGIS 2.4 Chugiak after running sudo apt-get update and sudo apt-get install qgis python-qgis qgis-plugin-grass.

I noticed the following error in the terminal when running sudo apt-get update:

W: GPG error: http://qgis.org jessie InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 073D307A618E5811
W: Failed to fetch http://qgis.org/debian-nightly/dists/jessie/main/binary-armhf/Packages  404  Not Found [IP: 104.27.139.220 80]

E: Some index files failed to download. They have been ignored, or old ones used instead.

I tried to fix this by adding the key manually (see http://hub.qgis.org/issues/8404):

gpg --keyserver keyserver.ubuntu.com --recv 073D307A618E5811
gpg --export --armor 073D307A618E5811 | sudo apt-key add -

Now sudo apt-get update throws a new error:

W: Failed to fetch http://qgis.org/debian-nightly/dists/jessie/InRelease  Unable to find expected entry 'main/binary-armhf/Packages' in Release file (Wrong sources.list entry or malformed file)

E: Some index files failed to download. They have been ignored, or old ones used instead.

Answer 1

According to http://qgis.org/debian-nightly/dists/jessie/main/, the QGIS binaries are for amd64 and i386 only. If you look into How to install GDAL and QGIS on a Raspberry Pi? you will learn that Raspbian needs armhf packages, which are not hosted at qgis.org. This is basically what the last error message tells you too.

So you have to use the old packages from http://www.raspbian.org/RaspbianRepository, or compile from source.

https://packages.debian.org/jessie-backports/qgis might be worth a try to get QGIS 2.14.9, but I have not yet managed to install those jessie backports.

For the nightly builds, compiling from source seems to be the only choice.