Well, I have my ~/.nzbget backed up of course, so I'd prefer to just install testing right over Stable like this.
The only concern I suppose is, IS there a possibility that I could corrupt/loose my existing download history if testing doesn't run correctly for me.
In other words, if testing doesn't work for me, can I simply reinstall v19.1 (or an earlier testing version) from the command line:
# sh nzbget-20.0-testing-rxxxx-bin-linux.run --destdir /usr/local/bin/
to "get back" to working order. ?
The other option you mentioned, installing into a separate directory, would also require me to configure a separate MAINDIR to avoid "mixing" the two versions' caches, queues, histories, etc ??