GitHub is dropping unauthenticated git protocol access in January 2022:

https://github.blog/2021-09-01-improving-git-protocol-security-github/#no-more-unauthenticated-git

Additionally, as of today (Nov. 2, 2021), they are doing "brown-outs" of such access which will intermittently break builds in the meantime.  Upstream OE/Yocto is going to work around this with a bitbake change that switches to protocol=https for github.com SRC_URIs where it is not specified.  In 3.5/Kirkstone, this will be accompanied by a warning to prompt fixing SRC_URIs.  This issue will track updating poky to get the bitbake change, and additionally updating the affected SRC_URIs in the meta-agl* repositories so we are prepared for upgrading to Kirkstone and address a request from upstream to quiet the warnings in the Yocto autobuilder tests of meta-agl-core's next branch.  It is an open question on how many AGL releases back we need to address this, as any that do not get the bitbake update will be unbuildable...