In my case, I created an emuMMC with Hekate 4.6.0 (my sysMMC, which I used to create the emuMMC, was on 21.0.0, so the emuMMC is also on 21.0.0). After creating it, I formatted the emuMMC system to completely detach it from the sysMMC.
Then I removed the PRODINFO data using NxNANDManager (I prefer deleting it rather than hiding it with exosphere, since if you only hide it with exosphere, Russian malware like DBI can still read your serial number). I don’t use exosphere, nor do I need to, since I have a clean PRODINFO thanks to NxNANDManager.
Then I installed sys-patch-1.5.8-esfix, and with it installed I used Awoo 1.3.6 to install legitimate NSPs: everything works as it should, none of the NSPs show “Please wait” or “Checking” at startup. Tested with several NSPs, after restarting, in airplane mode, or connected to WiFi.