I have a few questions :
- Is it mandatory to upgrade U-boot, on newer pbp ?
Yes, if you want assistance, I have no idea what manjaro uses, I do know it's on the EMMC.
- Can I know what version it has without serial port ? Missing config file for fw_printenv.
The Fedora one? It's 2021.04 with some fixes. The Fedora one outputs all the version information to the screen. No clue on manjaro one, I've never used it.
- Can I write U-boot from manjaro ?
No idea, I've never tested it.
- Is the pcie support is not already enabled in manjaro ? Could you just use it's kernel config like https://github.com/bengtfredh/pinebook-pro-fedora-installer.
See the bug report linked in my blog post, in short "No, it's not that straight forward"