While upgrading to rc5, it just occurred to me that I don’t have my handy aliases. My hunch is to add them to /etc/profile , but I note that OpenWrt is not a “regular” distro and maybe it is common to add then somewhere else like /etc/profile.d/aliases.sh, /etc/shinit or elsewhere.
That's exactly what I use, and I'd say it's "best practice" (in any case, just add something new in /etc/profile.d/).
You definitely don't want to modify /etc/profile directly, as that will prevent future upstream changes from being installed without you noticing that there's somehow a new /etc/profile-apk.new (or whatever it's called) and merging the diffs.
The "sanctioned" location is /etc/profile.d/ because the base-files package adds that automatically to the sysupgrade backup list (see /lib/upgrade/keep.d/base-files), so we don't have to keep telling people to modify sysupgrade.conf...