Apple’s latest macOS 27 developer beta stumbles on a boot‑selection glitch that blocks users from choosing alternate partitions or external drives. The bug, first spotted by the Asahi Linux community, keeps the Linux partition invisible in the boot picker and Startup Disk menu. Users can still access the data; the volume simply fails to appear as a boot target today.

Because macOS 27 alters how the recovery environment scans for valid OS volumes, the system no longer lists the Linux partition during startup. Asahi’s developers filed bug FB22994760 with Apple and patched the installer to block runs on macOS 27 until a workaround surfaces. The fix remains pending, leaving dual‑boot users stranded. This limitation also affects macOS versions on separate partitions, as early testing shows.

Until Apple resolves the issue, users who have a secondary macOS 26 installation can set it as the default Startup Disk to regain access to the Linux volume. The incident highlights the risks of installing early betas on multi‑OS setups and underscores the importance of waiting for the final public release before tweaking boot configurations.