Proposal for Mint 23: Restoring robust Hybrid ISO Boot (Legacy MBR/UEFI) for large USB media (>64GB)

[stefanolinux]

Dear Developers,

First of all, thank you for your immense and incredible volunteer work. Linux Mint is, in my experience, the number one operating system for flexibility and stability.

I have been following your project and the Linux world for 20 years. Following your gold standard and strict guidelines, I have always documented myself deeply before attempting anything; in fact, in 20 years, I have never posted a single question on the forums. I have always preferred to observe, study, and solve issues by myself. Today, however, I feel it is necessary to break my silence to share a critical structural issue born from intensive field testing, with the hope it can be evaluated for the upcoming Linux Mint 23.

I spent the last month testing the new Linux Mint 22 series compared to the Mint 21 series, specifically regarding the creation of Live USB systems with persistence on large media (128GB) used in hybrid development environments (Dual Boot EFI / Legacy MBR).

The Technical Problem (Observed Behavior):
Since the removal of isolinux/syslinux in favor of a pure GRUB2-hybrid layout in the ISO structure from version 22 onwards, creating a persistent live drive on high-capacity USB sticks (e.g., 128GB) with an MBR partition table results in a systematic boot failure (black screen or rescue prompt) when booting in Legacy mode on older or mixed-firmware motherboards (such as Z270 chipsets).

Conversely, under the exact same hardware conditions, older tools and distributions (Linux Mint 21, Rescuezilla, Boot-Repair) utilize a legacy-friendly hybrid boot sector geometry that works flawlessly across all devices, mapping the drive correctly regardless of partition size.

The Logic behind the Friction:
GRUB2 cloned via raw-image copy (dd style) onto large MBR structures frequently clashes with BIOS geometry limitations regarding block calculations past certain thresholds. While this streamlines the code for modern standard UEFI targets, it breaks the core promise of a truly universal "Swiss Army Knife" live system.

The Request (The Freedom of Choice Philosophy):
As an open-source community, our fundamental value should always be the option of choice. Since the days I was a Linux beginner, what I appreciated most about open source was the philosophical idea of software freedom and the absolute liberty of software application. Forcing a modern bootloader layout without a backward compatibility fallback completely locks out technicians and developers working in mixed environments, removing that essential freedom of application.

Furthermore, there is a real and urgent need in the wild. Nowadays, countless users are tired of traditional proprietary operating systems that are constantly exposed to massive data breaches and malware, leaving personal data completely vulnerable. Many of these people are actively approaching Linux as a safe haven, reading about its legendary ease of use and out-of-the-box compatibility. These new users urgently need a safe, frictionless environment to convert and secure their personal family libraries (photos, memories, private archives).

They are deeply frustrated by the rigid, exhausting "10-layer authentication" rules forced upon them by failing proprietary operating systems. Paradoxically, despite these suffocating restrictions, those central servers are constantly breached anyway. Newcomers look at Mint as an elastic, versatile, and complete haven—exactly like Linux Mint has always been up to version 21—to protect what matters most, without artificial and bureaucratic barriers. If we remove the hybrid boot fallback on larger drives, we risk repelling them with a discouraging black screen right at their first impact.

My proposal is to evaluate a baseline modification for future releases (Mint 23):

1. Re-introduce or maintain an automated legacy-fallback geometry module in the ISO generation code.
2. Provide a built-in GUI checkbox in the "USB Image Writer" tool to explicitly optimize target partitions for "Max Compatibility Legacy MBR", ensuring that the partition layout accommodates older BIOS limitations without requiring manual partition resizing in GParted/Gnome Disks.

I am eager to hear your technical thoughts on this architecture.

Best regards,
Stefano