EDIT: tldr - I was having issues creating a VM using Virtual Machine Manager on Bazzite Linux. Several responders chimed in that it’s likely because I’m using the flatpak version of VMM. I probably still could make it work on Bazzite somehow, perhaps w/ the help of distrobox, but instead I’ve fired up a VM on an old laptop running Linux Mint and everything is smooth sailing. Thanks to all who took some time to help me find a solution.

---

Original body:

Background: I’m looking to set up a virtual Debian server using Virtual Machine Manager, but I’m stuck on creating my first VM. I’m running Bazzite on my host machine if that makes any difference.

Steps to Reproduce the Issue:

1. Launch Virtual Machine Manager.
2. Click File > New Virtual Machine, which opens the “New VM - Step 1” window.
3. Select “Local install media” and click Forward, which brings me to “New VM - Step 2.”
4. Click “Browse…” which opens the “Locate ISO media volume” window:
5. Click “Browse Local,” which opens the file browser.
6. Choose ISO file (in my case, I’m using debian-12.11.0-amd64-netinst.iso) and click Select, which returns me to the “New VM - Step 2” window.
7. Because the OS is not detected automatically, I uncheck the “Automatically detect from the installation media / source” checkbox, start typing the word “debian” in the text box above it, and select Debian 12 from the pop-up selection menu.
8. Click Forward.

Actual behavior:

Input Error - Error setting installer parameters. Validating install media ‘/run/user/1000/doc/c0a3c3fc/debian-12.11.0-amd64-netinst.iso’ failed. Could not start storage pool: cannot open directory ‘/run/usr/1000/doc/c0a3c3fc’: Permission denied.

Expected behavior: Create the VM and boot into the ISO that I selected in previous steps.

What am I doing wrong? Thanks!