I have recently ported postmarketOS  to the HTC Desire Z. postmarketOS is a Linux distribution for mobile devices based on Alpine Linux and the primary platform for KDE's Plasma Mobile desktop.
Note that this work is nowhere near ready for productive use, at least not as a phone. It boots, the weston demo UI starts and you can ssh into it via USB or Wifi (use nmtui or nmcli to configure it), but that's pretty much it. I'm posting here in the hope that other developers might be interested in joining this effort. It might be useful as small server for personal use, perhaps to host a NextCloud instance or something like that.
For installation instructions, refer to the Installation Guide at  and the wiki page for the HTC Desire Z at . It should be possible to run postmarketOS without installing anything at all on the phone (other than an unlocked bootloader) by installing onto a microSD card and booting via the `fastboot boot` command.
P. S. If you're wondering why I didn't put this in the developers' section where it belongs: It's because I'm not allowed to post there due to being a new member, and for the same reason I can't post proper links. In order to prevent spam, new users are required to spam 10 posts in order to be able to do perfectly legitimate things. How ironic