How to create PPA packages for ARM or PowerPC in Launchpad?

To enable ARM builds

As of 8 November 2016, enabling ARM builds is self-service: you can change an option in the PPA settings to get it to build for any of the following architectures automatically (documentation link):

• AMD x86-64 (amd64)
• ARM ARMv8 (arm64)
• ARM ARMv7 Soft Float (armel)
• ARM ARMv7 Hard Float (armhf)
• Intel x86 (i386)
• PowerPC64 Little-Endian (ppc64el)

Log in and select "Change details" in the upper right corner of your PPA page. At the bottom of the page that follows, you'll see the above options that can be enabled. The following entries are ones that only an administrator of Launchpad can enable for your account.

• PowerPC (powerpc)
• IBM System z (s390x)

For these, you still request access on the forums, although searching the forum indicates that Canonical previously only did this under special circumstances (only if you're a Canonical employee or have a contract in place with Canonical). Another forum post suggests that powerpc and s390x builds should be available to all users by now, but I'm not sure if the security concerns of building your (possibly malicious) package on non-virtualized Canonical hardware have been resolved.

To build already published packages for ARM

Once you have enabled ARM in the Launchpad PPA settings, click "copy packages", and copy the packages to the same PPA (click on "copy existing binaries", so that Launchpad will simply copy the already built packages for amd64 or i386, and will only build new packages for ARM). When the next version of your package is released, you won't have to repeat this procedure, Launchpad will automatically build it for all architectures you had selected.