The DEB source packages appear to be missing for 10.2/10.3 from the repositories for both Debian and Ubuntu. The source packages are present for 10.1 (e.g. http://ftp.utexas.edu/mariadb/mariadb-10.1.30/repo/ubuntu/pool/main/m/mariadb-10.1/mariadb-10.1_10.1.30+maria-1~trusty.tar.gz)
Likewise, for the 10.2/10.3 repositories, the Sources.gz package list is empty. (See: http://ftp.utexas.edu/mariadb/mariadb-10.3.2/repo/ubuntu/dists/trusty/main/source/Sources.gz)
Perhaps the distribution model has changed to have people use the generic tar.gz source on these platforms - however, after an hour+ review of the documentation, I could find no mention of that change (if that's what it is). If this is intended, I would politely suggest that clear updates to documentation be made to make this clear.
Regardless of the intent here, not having the package source available in the Debian/Ubuntu repositories breaks apt functionality to retrieve source (e.g. "apt-get source"). Even if the intended avenues of source release have changed (e.g. to have everyone just download the .tar.gz generic linux source instead of the debian/ubuntu specific source), the borked functionality of apt-get that's induced by this is ... funky.
The end result is:
(Issue stems, ultimately, from wanting to build mariadb to include lz4 page compression. I was able to build 10.1 from source in the past. Will temporarily go back to 10.1 as those sources appear to be present.)
Thanks in advance everyone and please forgive me if I've overlooked something here.