I was getting this error on boot/launch: (after installing sys-patch)
Failed to apply nosigchk
Press power to continue
Press VOL to go to menu
When I pressed power it would boot fine and everything worked fine - it was just really annoying.
So I wanted to post my solution here in case it helps anyone else.
Before sys-patch, I was on fw 15.0.1 and hekate 6.0.1 / nyx 1.5.1 - a lot of things have changed in the past year or so, so I wanted to update to latest fw 16.0.3 and update all of atmosphere/hekate (then move to adding tesla menu, overclocking, and themes)
I had AIO updater but had never used it, and I found that sigpatches are no longer included with it, so I wanted to find the most efficient way to update. Thats when I found sys-patch and so I installed that and then ran the rest thru AIO updater. Everything updated fine, but I was getting the Failed to Apply nosigchk error above.
I had originally modded using the rentry guide but I could not find a fix that tied this with now migrating to using sys-patch.
After tons of searching I somehow got to editing hekate_ipl.ini (I'm sure plenty of you already know what the issue is - but it doesn't seem to be explicitly clear. Although I may have easily missed it - the amount of old/deprecated information about switch modding vs modern relevant information is pretty daunting and can make it quite overwhelming.)
I did not install fw16.0.3 sigpatches and I know in the sys-patch install it says recommended to still install sigpatches, but I've seen people say they haven't updated them so I figured may as well try it out now.
So the solution was to remove this line from hekate_ipl.ini:
kip1patch=nosigchk
It would be nice if this was included on the git readme. Or some sort of example hekate_ipl.ini file. I didn't see any reference in this thread either. Again my apologies if I overlooked it.
I somehow had the line cal0blank=1 also - I'm not sure what that did, I thought maybe it was related - I removed that first and everything still seems to work fine, so I left it out.
After removing the line above, I no longer get the error during launch, and all seems well. I hope this info helps!
Thanks to everyone who develops these mods!