Flatcar Container Linux and CoreOS not recognized as Linux platforms

[salgattll]

This is a bug report.

Expected behavior

Hosts running Flatcar Container Linux should have host detail information (private IP address, disk space, etc.) populated in the Fleet console, just like any other Linux distribution.

Actual behavior

Flatcar hosts enroll successfully and appear online in Fleet. Some host details populate (hardware model, OS name, memory, processor type), but platform-filtered detail queries — including network_interface_unix (IP/MAC), disk space, and others — are never sent to the host. Live queries for the same data return results correctly.

Steps to reproduce

1. Enroll a Flatcar Container Linux host with Fleet (via Orbit or standalone osquery)
2. Observe the host in Fleet console — Status shows "Online", some vitals populate
3. Note that Private IP address is blank, Disk space shows "No data available"
4. Run a live query for SELECT * FROM interface_addresses — it returns data correctly

Root cause

Flatcar reports platform=flatcar and platform_like=coreos via osquery's os_version table. Neither flatcar nor coreos is present in HostLinuxOSs in server/fleet/hosts.go. This causes PlatformFromHost("flatcar") to return "" (empty string), and RunsForPlatform to skip all Linux-platform-filtered detail queries.

Proposed fix

Add "flatcar" and "coreos" to:

• HostLinuxOSs in server/fleet/hosts.go
• HostNeitherDebNorRpmPackageOSs in server/fleet/hosts.go (neither distro uses deb or rpm)
• HOST_LINUX_PLATFORMS in frontend/interfaces/platform.ts
• Test cases in server/fleet/hosts_test.go
• Platform lists in docs/Contributing/product-groups/orchestration/understanding-host-vitals.md

This is the same pattern used for other community-added distributions (tuxedo #19011, neon #28977, manjaro-arm #34357, etc.)

Context

• Fleet version: v4.81.1 (fleetctl), server v4.64.2
• osquery version: 5.21.0
• Flatcar Container Linux version: 4459.2.4
• Orbit version: 1.53.0
• Deployment method: systemd-sysext on Flatcar with Orbit managing osqueryd

Happy to submit a PR for this.