kup doesn't work in `--no-daemon` (single user) Nix installs

Start by reproducing the Debian 12 single-user Nix setup with the documented dent and kup commands, then inspect kup's Nix profile installation and cache/substituter handling. Done means kup installs successfully without conflicting profile entries, repeated prompts, or unwanted /etc/nix configuration, and the installed K commands are available.

I've been testing in fresh Debian 12 containers created with dent. You can replicate these with:

cd $HOME/my-checkouts/         # use whatever path you like here
git clone https://github.com/cynic-net/dent
cd ~/.local/bin
ln -s dent $HOME/my-checkouts/dent/bin/dent

and then running

dent -B debian:12 -S my-checkouts deb12nodaemon

and the like. You can read-write share a directory under you home dir other than my-checkouts by specifying something different there (or just leave it out if you're going to use only things local to the container), and once you've done the initial container creation with -B you can re-enter the container any time with just dent deb12nodaemon. You can also substitute, e.g., ubuntu:22.04 or ubuntu:24.04 for debian:12 if you prefer to use those userlands.

Within one container I installed Nix with curl -sS -L https://nixos.org/nix/install | sh -s -- --daemon (single-user) and the other curl -sS -L https://nixos.org/nix/install | sh -s -- --daemon (multi-user). In the multi-user container you must of course sudo -s and nix-daemon to start the daemon.

In both, curl https://kframework.org/install | bash seems to work fine. kup install k --version v7.1.80, and then choosing option 1 at the prompt dealing with the "caches" (by which I gather it means "substituters"), things install ok on the multi-user Nix install.

But on the single-user Nix install I end up with problems like:

c$ kup install k --version v7.1.80
 ⌛ Building 'k' ...
error: An existing package already provides the following file:

         /nix/store/jrv1fncf56v6mfqxms66khpw77sykms3-nix-2.24.1/share/man/man1/nix-channel.1.gz

       This is the conflicting file from the new package:

         /nix/store/rzngdyihwcdnlpyxv4nfrhl1mhzbmvkc-profile/share/man/man1/nix-channel.1.gz

       To remove the existing package:

         nix profile remove nix

       The new package can also be installed next to the existing one by assigning a different priority.
       The conflicting packages have a priority of 5.
       To prioritise the new package:

         nix profile install /nix/store/rzngdyihwcdnlpyxv4nfrhl1mhzbmvkc-profile --priority 4

       To prioritise the existing package:

         nix profile install /nix/store/rzngdyihwcdnlpyxv4nfrhl1mhzbmvkc-profile --priority 6
Command '['nix', 'profile', 'install', 'github:runtimeverification/k/f73063d8260ca1a40c9e850db60f3a9a1dcb691f?narHash=sha256-pFOw/vJ6g9bM8PzfiaZtSc89Vohmcu/rCkxZiQAeAEo%3D#packages.x86_64-linux.k', '--extra-experimental-features', 'nix-command flakes']' returned non-zero exit status 1.

❗ The operation could not be completed.
   See the error output above (try re-running this command with '--verbose' for more detailed logs) ...
1 c$ nix profile remove nix
error: experimental Nix feature 'nix-command' is disabled; add '--extra-experimental-features nix-command' to enable it
1 c$ nix --experimental-features 'nix-command flakes' profile remove nix
removing 'nix'
c$ kup install k --version v7.1.80
 ⌛ Building 'k' ...
error: An existing package already provides the following file:

         /nix/store/3p9j3a7mqh913mr9iplnimxdn89x02lg-python3.9-kup-0.2.4/lib/python3.9/site-packages/kup-0.2.4.dist-info/METADATA

       This is the conflicting file from the new package:

         /nix/store/rzngdyihwcdnlpyxv4nfrhl1mhzbmvkc-profile/lib/python3.9/site-packages/kup-0.2.4.dist-info/METADATA

       To remove the existing package:

         nix profile remove kup

       The new package can also be installed next to the existing one by assigning a different priority.
       The conflicting packages have a priority of 5.
       To prioritise the new package:

         nix profile install /nix/store/rzngdyihwcdnlpyxv4nfrhl1mhzbmvkc-profile --priority 4

       To prioritise the existing package:

         nix profile install /nix/store/rzngdyihwcdnlpyxv4nfrhl1mhzbmvkc-profile --priority 6
Command '['nix', 'profile', 'install', 'github:runtimeverification/k/f73063d8260ca1a40c9e850db60f3a9a1dcb691f?narHash=sha256-pFOw/vJ6g9bM8PzfiaZtSc89Vohmcu/rCkxZiQAeAEo%3D#packages.x86_64-linux.k', '--extra-experimental-features', 'nix-command flakes']' returned non-zero exit status 1.

❗ The operation could not be completed.
   See the error output above (try re-running this command with '--verbose' for more detailed logs) ...
1 c$ nix --experimental-features 'nix-command flakes profile remove kup
removing 'github:runtimeverification/kup#packages.x86_64-linux.kup'
c$ kup install k --version v7.1.80
 ⌛ Building 'k' ...
 ✅ Successfully installed 'k' version 
github:runtimeverification/k/f73063d8260ca1a40c9e850db60f3a9a1dcb691f?narHash=sha256-pFOw/vJ6g9bM8PzfiaZtSc89Vohmcu/rCkxZiQAeAEo%3D#packages.x86_64-linux.k 
(v7.1.80).
c$ kup list
┌──────────────────────┬───────────────────┬──────────────┐
│ Package name (alias) │ Installed version │ Status       │
├──────────────────────┼───────────────────┼──────────────┤
│ kup                  │                   │ 🔵 available │
│ k                    │                   │ 🔵 available │
│ kavm                 │                   │ 🔵 available │
│ kevm                 │                   │ 🔵 available │
│ kplutus              │                   │ 🔵 available │
│ kmir                 │                   │ 🔵 available │
│ kontrol              │                   │ 🔵 available │
│ kmxwasm              │                   │ 🔵 available │
└──────────────────────┴───────────────────┴──────────────┘
c$ kompile --version
bash: kompile: command not found
c$

Earlier it was also giving me the prompt about the "caches" and me being an untrusted user, which doesn't seem relevant in a single-user installation, and regardless of what I answered it would always give me the same message and prompt a second time, until I finally selected option 1 twice, at which point is created the non-existent /etc/nix/ directory (which I believe should not exist in a single-user installation) and the nix.conf in it (which I believe is not used in a single-user installation).