Well blocking OTA / renaming OTA binaries is usually done by KUAL extension and installing KUAL is done using MRPI...
"Advanced" approach would be skipping all that (MRPI and KUAL) and taking the "rename.sh" (or whatever exact filename) script file from "renameotabin" KUAL extension and renaming it to "RUNME.sh" (notice the uppercase letters), copy the file into "root" / top level of kindle removable drive and then executing that by typing
;log runme into searchbar OR making a "scriptlet" out of it by placing it into "documents" folder.
Before you're able to do that you need to install the hotfix since that's what sets up both ";log" commands and "scriptlet" handler.
Afterwards if I were you I would also make sure to check if OTA binaries were actually renamed by using "Check OTA status" scriptlet:
https://scriptlets.notmarek.com/
As for Amazon pushing that "DRM fix" I'm not sure that renaming OTA binaries would even be able to stop THAT from happening, since as I understood it that has happened to people without a firmware update being installed, even on Kindle models that haven't gotten firmware update in years and years?
Someone would need to investigate and determine precise mechanism Amazon uses for that and how to block that.