Any desktop file running ephy with --application-mode command line options should work. It doesn't need to provide the profile directory, it will be built from the desktop file info, and created on first run.
8748d40 web-app: Add support for system-wide installed web apps
lib/ephy-web-app-utils.c | 125 ++++++++++++++++++++++++++++++++++++++++++++--
lib/ephy-web-app-utils.h | 7 +++
src/ephy-main.c | 49 +++++++++---------
3 files changed, 150 insertions(+), 31 deletions(-)
Upstream: git.gnome.org