Update October 24th, 2023: This is now unnecessary, as patches have been released for 17.0.0. if you are on 17.0.0, I recommend updating your sigpatches instead of downgrading.
Disclaimer: While these steps should be safe, I am not responsible if you mess up your emummc, or have save file compatibility issues by downgrading from 17.0.0. Your console is your responsibility.
To start, you may have noticed sigpatches do not support FW 17.0.0 yet. This is due to significant changes in the FS module in 17.0.0 that are breaking current methods of generating FS sigpatches. We are still waiting on the changes to be researched and new sigpatches made.
If your emummc is on 17.0.0, either by you upgrading it without knowing better, or because your sys was on 17.0.0 when you made the emu, you will need to downgrade to 16.1.0 for working patches.
Note that you DO NOT need to run AMS 1.5.5 for sigpatches to work on FW 16.1.0. While the sigpatches do not support 1.6.1 or 1.6.0, the Sys-Patch sysmodule included with the sigpatches does support patching LDR on any AMS version. Thus, running AMS 1.6.1 with emuMMC 16.1.0 is perfectly fine to do.
Note 2: I do not recommend downgrading your sysMMC (due to it being ban-bait, and mismatched fuses), unless you are running a banned switch with a sysCFW-only setup and upgraded on accident. If you have an emuMMC, you should keep the emu on 16.1.0 and leave your sys on 17.0.0 if it is already updated.
Let's get started:
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Download firmware 16.1.0 from Ecchi's Firmware Archives: e.cchi.me
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On Ecchi's website, click "All-Purpose Mirror Service", then "archive" -> "nintendo" -> "switch" -> "firmware" and download "Firmware 16.1.0.zip"
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Get your SD card from the switch, and create this folder on your SD root:
Firmware 16.1.0. Extract the contents of the zip file to the folder you just created. Place SD back in system, inject Hekate, and boot emuMMC using Hekate 6.0.7 + AMS 1.6.1. -
Open HBMenu via the album if you do not have any working titles. If you do, launch via title takeover instead by holding R while opening an app/game.
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Launch Daybreak in HBMenu.
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Tap on "Install" and navigate to /Firmware 16.1.0 on your SD. Tap on "Continue" and then "Preserve settings".
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If it is available choose "Install (FAT32 + exFAT)", otherwise "Install (FAT32)" and then "Continue".
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Wait until Daybreak completes installing your firmware.
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Once it completes, it will ask if you want to reboot. Tap "Reboot".
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Once rebooted, launch into emuMMC again and verify your system works. You can verify your system has been properly downgraded in Settings -> System. The version string should now be
16.1.0 | AMS 1.6.1 | E.
If you don't already have them on your SD, you can grab the latest sigpatches from the usual sigmapatches.coomer.party site. Simply extract the contents of Sigpatches.zip to your SD card root, merging and replacing files when asked.