subprojects aren't buildable with Ubuntu 18.04 LTS
According to the comments in meson.build, the libdazzle and libhandy subprojects are present to allow Epiphany to be built on Ubuntu 18.04 LTS.
However, both subprojects require gtk 3.24 and Ubuntu 18.04 LTS only has gtk 3.22.30. It's not very feasible to upgrade gtk to 3.24 in Ubuntu 18.04 LTS because the new gtk version requires newer versions of other projects like pango.
As I commented previously, the libhandy subproject is still useful for Debian 10 "Buster".
Suggestion 1
- Drop the libdazzle subproject
- Update the comment to mention Debian 10 instead of Ubuntu.
References
- libdazzle 3.30 requires https://developer.gnome.org/gtk3/stable/GtkEventControllerMotion.html
- libhandy wants gtk 3.24.1 for updated (Adwaita?) styles