Direct links cannot be provided but other questions are fine, like how to install them or errors that you encounter while running them. The usually culprit for NSPs not working is that they need
signature and ES patches to load when using Atmosphere CFW. They need to be in the /Atmosphere folder and the official GitHub Atmosphere.zip does not include them by default. ReiNX and SX OS do not need them/have them built in.
Each firmware has a fuse "count" associated with it, not a particular fuse.
https://switchbrew.org/wiki/Fuses#Anti-downgrade
Here is the exactly what happens:
The Switch uses a common anti-downgrade technique that utilizes microscopic fuses built into the CPU (ie. fuses that cannot be replaced). When turning on the Switch through regular means, the firmware performs a fuse check. On boot the following process is performed:
- The bootloader will first check for how many fuses are burnt.
- If there are less fuses burnt than the bootloader expects for a firmware version, the bootloader will enable fuse programming, burn up fuses up to as many as it expects, write the expected value to fuse indexes 0x3A and 0x3C, disable fuse programming and reboots via a watchdog timer checking for panic value 0x21. (new firmware added to an older switch - normal update)
- On a subsequent boot, after the anti-downgrade fuses are checked again, the PMC_RST_STATUS register (0x7000E5B4) is checked and if set to 0x01 (watchdog reset) the PMC_SCRATCH200 register (0x7000EC40) will be checked for the panic value 0x21. PMC_RST_STATUS will only be set back to 0 (power on reset) if the fuse count matches the new expected value, otherwise the system will panic again.
- If there are exactly enough fuses burnt as the firmware expects, it will allow the Switch to load the firmware. (normal reboot)
- If there are too many fuses burnt, the Switch’s native bootloader will panic immediately, not allowing the firmware to boot. (older firmware boots a newer switch - system has been downgraded, so refuses to boot)
The bootloader cannot start reading the required fuse count associated with the firmware when the Switch is put into recovery mode (RCM) because entering recovery mode happens prior to the bootloader reading from the firmware on the sysNand. This has the effect of "skipping" the part of the bootloader that burns fuses. Thus, if automatic recovery mode (RCM) is enabled, no fuses will ever be burnt. Thus, because the rcm bug/Fusée Gelée exploit happens prior to the fuse check, any switch vulnerable to FG will forever be vulnerable to it. The fuse count does not matter for CFW at all.
The sole purpose of the fuses is to prevent downgrading and, on a FG vulnerable switch, they do not work. Downgrading from a OFW 8.1-> 4.1.0 is 100% do-able and the firmware will work normally because the fuse-check is bypassed completely when entering recovery mode.
Boot->recovery mode->[any firmware version].
Without going into recovery mode, the fuse check will occur and the firmware will not normally boot. The switch just shuts off. What people describe as a "brick" when downgrading is either misinformation, from people not understanding what is happening, or refers to having to enter recovery mode manually, or having to enable autoRCM, which itself can be described as a "controlled brick".