Per Plamen:
https://community.braxtech.net/t/how-to-manually-install-or-update-your-os-on-your-brax3/46
https://community.braxtech.net/t/how-to-change-the-imei-number-on-your-brax3/30
These are my journeys in the process (it is NOT simple):
https://community.braxtech.net/t/brax3-in-hand-imei-needed/1116
https://community.braxtech.net/t/help-please-with-sp-flash-tool-in-linux-and-terminal-commands/1816
EDIT: Be aware, the version of LunarOS that is provided is a “userdebug” version, which has a “watermark” on the phone upper left corner at all times. It is a bit in the way for browser address bar entry, but I’m living with it because the phone works. Instructions were provided for removing it but it requires rooting the phone, which I am not doing at this point.
Serial Console is enabled, which directs you to check bootloader to disable…it appears on the notification screen also at all times, like Trebuchet does in iode. Again, living with this after doing a bit of research.
I asked Rob on brax.me if there was someone I could ask a few questions of (re: Lunar) he said “wait for the project open source to be published shortly and you can interact with the devs”. So this is what I am waiting for, hoping there is resolution for those 2 issues without rooting the phone.