Although the option debug-level is listed by gpgconf --list-options gpg, the application of those defaults causes an error:
gpgconf: External verification of component gpgsm failed
gpgconf: could not commit changes: Invalid argument
gpgconf: fatal error (exit status 1)
this is true for other components also.
--apply-defaults is an obsolete option because we now have global config files. I would also like to get rid of --debug-level but that won't be easy. Using --debug LIST_OF_DEBUG_FLAGS is a more versatile way of specifying debug options.
From which version on there will be global config files? The only info I found was about /etc/gnupg/gpgconf.conf and /etc/skel/.gnupg/* to manage presets.
$ gpg --debug 0 --gpgconf-test gpg: reading options from '/etc/gnupg/gpg.conf' gpg: reading options from '/home/foo/.gnupg/gpg.conf' gpg: reading options from '[cmdline]' gpg: reading options from '/etc/gnupg/common.conf' gpg: reading options from '/home/foo/.gnupg/common.conf'
This is how 2.3 reads options. 2.2 does the same except for the common.conf.