Just an FYI, that something seems to be amiss with Kernel 6.6.

I run OpenSUSE Tumbleweed on my Darter Pro.

I've found that, starting with early kernel 6.6 releases (and up to at least 6.6.1) the path '/sys/class/leds/system76_acpi::kbd_backlight` no longer exists, and the keyboard backlight is no longer controllable (and defaults to off). Kernel 6.5.9 is the most recent version I've found that works.

There are no relevant kernel configuration changes that I can see between then and now, as packaged by opensuse.

The following is in my dmesg buffer post-boot on this 6.6.1 kernel:

[   16.203995] sysfs: cannot create duplicate filename '/devices/LNXSYSTM:00/LNXSYBUS:00/17761776:00/leds/system76_acpi::kbd_backlight/color'
[   16.204003] CPU: 0 PID: 1232 Comm: (udev-worker) Not tainted 6.6.1-1-default #1 openSUSE Tumbleweed 0c6504f7d2c054731662677f280b3e0e68eca996
[   16.204007] Hardware name: System76 Darter Pro/Darter Pro, BIOS 2022-11-21_b337ac6 11/14/2022
[   16.204009] Call Trace:
[   16.204012]  
[   16.204015]  dump_stack_lvl+0x47/0x60
[   16.204023]  sysfs_warn_dup+0x5a/0x70
[   16.204028]  sysfs_add_file_mode_ns+0x11a/0x130
[   16.204031]  internal_create_group+0x115/0x3a0
[   16.204035]  internal_create_groups+0x42/0xa0
[   16.204038]  device_add+0x597/0x890
[   16.204042]  ? kstrdup+0x4c/0x70
[   16.204045]  device_create_groups_vargs+0xce/0xf0
[   16.204049]  device_create_with_groups+0x43/0x60
[   16.204053]  led_classdev_register_ext+0x1c1/0x430
[   16.204057]  ? devm_led_classdev_register_ext+0x3a/0x90
[   16.204060]  ? __pfx_devm_led_classdev_release+0x10/0x10
[   16.204063]  devm_led_classdev_register_ext+0x50/0x90
[   16.204066]  system76_add+0x18b/0x440 [system76_acpi 6778ab907a326eeb6d97e8c957cf2c7d3aa12d04]
[   16.204074]  ? sysfs_do_create_link_sd+0x6e/0xe0
[   16.204077]  acpi_device_probe+0x47/0x130
[   16.204082]  really_probe+0x19b/0x3e0
[   16.204085]  ? __pfx___driver_attach+0x10/0x10
[   16.204088]  __driver_probe_device+0x78/0x160
[   16.204090]  driver_probe_device+0x1f/0x90
[   16.204093]  __driver_attach+0xd2/0x1c0
[   16.204095]  bus_for_each_dev+0x74/0xc0
[   16.204096] input: PC Speaker as /devices/platform/pcspkr/input/input9
[   16.204097]  bus_add_driver+0x116/0x220
[   16.204100]  driver_register+0x59/0x100
[   16.204103]  ? __pfx_system76_driver_init+0x10/0x10 [system76_acpi 6778ab907a326eeb6d97e8c957cf2c7d3aa12d04]
[   16.204109]  do_one_initcall+0x47/0x310
[   16.204114]  ? kmalloc_trace+0x2a/0xa0
[   16.204117]  do_init_module+0x60/0x240
[   16.204121]  __do_sys_init_module+0x17f/0x1b0
[   16.204125]  ? __seccomp_filter+0x31b/0x510
[   16.204129]  do_syscall_64+0x5d/0x90
[   16.204132]  ? do_syscall_64+0x6c/0x90
[   16.204134]  ? do_syscall_64+0x6c/0x90
[   16.204136]  ? do_user_addr_fault+0x30f/0x660
[   16.204140]  ? exc_page_fault+0x71/0x160
[   16.204143]  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
[   16.204147] RIP: 0033:0x7f7e7ed199de
[   16.204163] Code: c3 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 49 89 ca b8 af 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 12 14 0d 00 f7 d8 64 89 01 48
[   16.204165] RSP: 002b:00007fff7a559488 EFLAGS: 00000246 ORIG_RAX: 00000000000000af
[   16.204169] RAX: ffffffffffffffda RBX: 000055a52271d0b0 RCX: 00007f7e7ed199de
[   16.204170] RDX: 00007f7e7f41c061 RSI: 0000000000008323 RDI: 00007f7e7e406010
[   16.204172] RBP: 00007f7e7f41c061 R08: 0000000000000630 R09: 0000000000000000
[   16.204173] R10: 00007f7e7edebb20 R11: 0000000000000246 R12: 0000000000020000
[   16.204175] R13: 0000000000000000 R14: 000055a52271f950 R15: 0000000000000000
[   16.204177]  
[   16.204208] System76 ACPI Driver: probe of 17761776:00 failed with error -17