The Mobian project aims to bring Debian on mobile devices. It is maintained by 2 distinct (but overlapping) teams:
the Mobian team is responsible for maintaining downstream packages (containing non-upstreamable patches and/or not ready for inclusion into Debian) and non-packaging tasks, such as image generation and distribution
the DebianOnMobile team maintains packages which are already part of the Debian archive.
Also see Mobian on pine64 wiki
Project wiki: https://wiki.mobian.org/
IRC: #mobian on OFTC
For installation instructions see InstallingDebianOn/PINE64/PinePhone