Installing on Debian
For a desktop system, the next stable is probably the better choice, called Debian testing, currently version 10 with codename Buster. Otherwise, Siril should still work with Debian 8 Jessie and 9 Stretch. You may want to build a .deb package instead of using a non-packaged version, in that case see this help. In particular, to install dependencies, you can use the command:
apt build-dep siril