Unable to format secondary nvme ssd after installing Steam OS

Your system information

• Steam client version: 1782861641
• SteamOS version: 3.8.14
• Opted into Steam client beta?: [Yes/No] No
• Opted into SteamOS beta?: [Yes/No] No
• Have you checked for updates in Settings > System?: [Yes/No] Yes

Please describe your issue in as much detail as possible:

Describe what you expected should happen and what did happen.

Steps for reproducing this issue:

1. I have two nvme ssds installed on the PC (AMD 9800x3d and RX 9070xt ; B650-CX R2.0 motherboard)
2. When I install SteamOS from a USB stick, with the wipe function, it doesn’t give any choice of disk to install and since I’ve reinstalled it several times now, the target nvme ssd changes randomly from install to install.
3. My issue is that once installed, the secondary ssd takes time to be recognized when in Big Picture Mode. When it is finally detected, I cannot format the ssd. When pressing Y I get an error message : FORMAT ERROR Failed to format. Try again - if it continues to fail we recommend you perform a full shut down before removing the storage media.
4. In Desktop Mode I have formatted the secondary ssd in ext4 but I still got the same error message when trying to "format" it in Big Picture Mode.
5. In desktop mode, in the Steam app, I can add the secondary drive to the storage but this doesn’t translate (all the time ; it seems random) to the Big Picture Mode. In Big Picture Mode, sometimes it will show me the content of the drive and sometimes it will give me the option to format it. Which fails. Besides, this secondary ssd disappears after a reboot.
6. What I expect the Steam OS installer to do is first to allow me to chose on which drive to install Steam OS. Then allow me to decide what to do with any secondary drive.
7. What I expect in Steam OS is that it automounts any secondary drive and allows me to format it. (In case I add a new drive later)
8. I have seen that there were similar issues with some SD cards. Sorry for the redundancy. But I am surprised that a secondary internal drive isn’t detected during the installation process and automatically dealt with (do nothing/dual boot/format/…). As a side note, the system was running flawlessly without the secondary ssd. And both nvme ssds are healthy and are both able to run Steam OS and games.
9. Thanks for your help.

Start by reproducing the installer wipe flow with two NVMe SSDs, then compare secondary-drive detection and formatting in Desktop Mode and Big Picture Mode across a reboot. The issue is resolved when the installation target can be selected and a secondary internal drive is consistently detected, mounted, and formatted as expected.