Add Keychron K2 Max ISO RGB support

[0x0ndra]

Description

This PR adds VIA support for the Keychron K2 Max ISO RGB variant.

Why This PR Is Needed

⚠️ Issue with Official Keychron Downloads:

The official Keychron firmware/JSON download page has an incorrect download link for the K2 Max ISO RGB variant:

• Page: https://www.keychron.com/pages/firmware-and-json-files-of-the-keychron-qmk-k-pro-and-k-max-series-keyboards
• Problem: When attempting to download the "K2 Max ISO RGB" JSON file, the link incorrectly downloads the "K2 Max ISO White" variant instead
• Impact: Users with K2 Max ISO RGB keyboards cannot properly configure their device with VIA using the official download

This community-contributed JSON file provides the correct configuration for K2 Max ISO RGB users until Keychron fixes their download link.

Product Details

• Model: Keychron K2 Max ISO RGB
• Product ID: 0x0A21
• Vendor ID: 0x3434
• Layout: ISO (European layout with large Enter key)
• Variant: RGB (full RGB matrix backlight)
• Firmware Version: v1.1.0 (2025-03-11)

Features Included

Keyboard Layout

• Full ISO layout support with proper key positioning
• 84-key layout (75% form factor)
• 6×16 matrix configuration

RGB Matrix Lighting Controls

• Brightness: Adjustable range 0-255
• Effects: 23 lighting effects including:
  • Solid Color, Breathing
  • Cycle modes (All, Left-Right, Up-Down, Pinwheel, Spiral)
  • Rainbow effects (Moving Chevron, Beacon)
  • Reactive modes (Simple, Multiwide, Multinexus)
  • Special effects (Typing Heatmap, Digital Rain, Pixel Rain, Jellybean Raindrops, Splash)
• Effect Speed: Conditional speed control (0-255)
• Color Picker: HSV color selection for compatible effects

Custom Keycodes

macOS-specific:

• Mission Control
• Launchpad
• Siri
• Screenshot
• Left/Right Option
• Left/Right Command

Windows-specific:

• Task View
• File Explorer
• Cortana

Wireless Connectivity:

• Bluetooth Host 1/2/3 switching
• 2.4G wireless mode toggle
• Battery level indicator

Testing & Verification

✅ Tested and confirmed working with:

• Physical keyboard: Keychron K2 Max ISO RGB
• Firmware: v1.1.0 (build date: 2025-03-11-16:29:03)
• VIA version: V3
• Keychron Launcher info verified:
  • PID: 0A21
  • VID: 3434
  • RGB: Y (Yes)

✅ All functionality verified:

• Key remapping works correctly for all positions
• RGB lighting controls functional in VIA
• Custom keycodes (BT switching, macOS/Windows keys) working
• Layout rendering correct in VIA interface

Technical Differences from White Variant

RGB variant (0x0A21) vs White variant (0x0A24):

Feature	RGB Variant	White Variant
Product ID	0x0A21	0x0A24
Lighting Menu	RGB Matrix controls (brightness, 23 effects, speed, color)	Backlight controls (brightness, speed)
Custom Keycodes	Standard set (no lighting keycodes)	Includes BL_SPI, BL_SPD for backlight
Menus Section	Required (RGB controls)	Optional/different

File Structure

v3/keychron/k2_max/
└── k2_max_iso_rgb.json

Additional Notes

• This is the first K2 Max variant added to the VIA keyboards repository
• JSON structure follows established Keychron conventions (matching Q-series, V-series format)
• Menu structure based on other Keychron RGB keyboards (e.g., V5, C1 Pro RGB)
• No ANSI variant included in this PR (ANSI RGB uses different Product ID: 0x0A20)

Related Links

• Keychron official page (with incorrect download): https://www.keychron.com/pages/firmware-and-json-files-of-the-keychron-qmk-k-pro-and-k-max-series-keyboards
• Product page: https://www.keychron.com/products/keychron-k2-max-qmk-via-wireless-custom-mechanical-keyboard

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Note to maintainers: This JSON has been thoroughly tested and is ready to merge. Once merged, K2 Max ISO RGB users will be able to use VIA without manually loading JSON files.