@lolek If you don’t see the gigantic benefits of having nix on SailfishOS, then I guess it is not for you, because you haven’t yet run into a situation where you needed it.
Sure, there is pkcon and zypper on SailfishOS. But good luck installing anything recent or custom with it. The jolla repos contain what’s necessary to run the OS, not more. Many of the core tools are outdated. GnuPG is extremely out of date, due to licensing issues IIUC. Want to use tmux? You have to use some random build off OpenRepos that doesn’t work. Or breaks after the next update. Same for all the Python stuff. Same for other shells like fish. The list is infinite, as there is a quasi infinite amount of new software being made that’s just not in the jolla repos or openrepos. Packaging dependencies and software for OpenRepos or elsewhere is very tedious in my experience. And outdated fast.
With nix, there’s a gigantic community packaging pretty much everything. You don’t have to do it. Nix packages will just work across SailfishOS updates. They are self-contained. With nix you can get proper up to date encryption tools (see my GPG example above).
For me, having a Linux phone is about sharing workflows and tools across machines. I do time tracking from the terminal with timewarrior and can amend it from the phone. I manage my finances with hledger and can emergency-analyse it on the phone. I sync files with git-annex and can have my phone be part of it. The list goes on. All of this is so much easier now with nix. I had to package or build everything myself before. Now I don’t and it’s awesome. 