I would love to NEVER use it but there are a few sites - namely Canada's news networks - that won't work without it.
So I was faced with trying to get it working in Debian Stretch. Here's what I've done so far:
- Firefox - it should support the NPAPI version installed by flashplugin-installer. However the flashplugin-installer is buggy and won't download the plugin. I got the plugin in a package from Adobe, unpacked it, installed the plugin in the right directory, geeked around with permissions and Debian alternatives and it works. I expect when they update the flashplugin-installer everything will break again, Life in the fast lane.
- Chromium - requires the PPAPI version. The installer isn't available in the Testing repos for some reason. I cannot find out how and where to manually install the plugin in Chromium. The only workaround is to install Chrome itself which comes in a nice deb package. Flash works fine in Chrome.