user7900: I'm using Ubuntu 20.04.5 with an 11th Gen Intel® Core™ i7-1195G7 @ 2.90GHz × 8.
After cloning the plutus-apps repo and setting my nix config, i can't get pass the following nix-shell error:
trace: To materialize project.plan-nix for haskell-project entirely, pass a writable path as the `materialized` argument and run the 'updateMaterialized' script in 'passthru'.
warning: error: unable to download 'https://hydra.iohk.io/nix-cache-info': Timeout was reached (28); retrying in 280 ms

my etc/nix/nix.conf is set to the parameters from README.adoc :
substituters        = https://hydra.iohk.io https://iohk.cachix.org https://cache.nixos.org/
trusted-public-keys = hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ= iohk.cachix.org-1:DpRUyj7h7V830dp/i6Nti+NEO2/nhblbov/8MW7Rqoo= cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
extra-experimental-features = nix-command flakes 


any advice appreciated
Updates:
The compilation with nix-shell completed bringing me to
[nix-shell:~/Documents/Plutus/plutus-apps]$
However, along the way I get lots of warnings. Should I be concerned? For example:
System/Remote/Snap.hs:7:1: warning: [-Wunused-imports]
    The import of ‘<$>’ from module ‘Control.Applicative’ is redundant
  |
7 | import Control.Applicative ((<$>), (<|>))
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


user7345: The nix cache is now located at cache.iog.io
With a /etc/nix/nix.conf (or ~/.config/nix/nix.conf) that looks like this:
experimental-features = nix-command flakes
allow-import-from-derivation = true
substituters = https://cache.nixos.org https://cache.iog.io
trusted-public-keys = hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ= cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=

then you should have the binary cache from IOG working again.
(you many need to log out and log back in and or restart the nix daemon to get these changes to take)
Doc source

7900: <p>I'm using <code>Ubuntu 20.04.5</code> with an <code>11th Gen Intel® Core™ i7-1195G7 @ 2.90GHz × 8</code>.</p>
<p>After cloning the plutus-apps repo and setting my nix config, i can't get pass the following nix-shell error:</p>
<pre><code>trace: To materialize project.plan-nix for haskell-project entirely, pass a writable path as the `materialized` argument and run the 'updateMaterialized' script in 'passthru'.
warning: error: unable to download 'https://hydra.iohk.io/nix-cache-info': Timeout was reached (28); retrying in 280 ms
</code></pre>
<p>my etc/nix/nix.conf is set to the parameters from README.adoc :</p>
<pre><code>substituters        = https://hydra.iohk.io https://iohk.cachix.org https://cache.nixos.org/
trusted-public-keys = hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ= iohk.cachix.org-1:DpRUyj7h7V830dp/i6Nti+NEO2/nhblbov/8MW7Rqoo= cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
extra-experimental-features = nix-command flakes 

</code></pre>
<p>any advice appreciated</p>
<p>Updates:</p>
<p>The compilation with nix-shell completed bringing me to</p>
<p><code>[nix-shell:~/Documents/Plutus/plutus-apps]$</code></p>
<p>However, along the way I get lots of warnings. Should I be concerned? For example:</p>
<pre><code>System/Remote/Snap.hs:7:1: warning: [-Wunused-imports]
    The import of ‘&lt;$&gt;’ from module ‘Control.Applicative’ is redundant
  |
7 | import Control.Applicative ((&lt;$&gt;), (&lt;|&gt;))
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
</code></pre>
 7345: <p>The nix cache is now located at cache.iog.io</p>
<p>With a <code>/etc/nix/nix.conf</code> (or <code>~/.config/nix/nix.conf</code>) that looks like this:</p>
<pre><code>experimental-features = nix-command flakes
allow-import-from-derivation = true
substituters = https://cache.nixos.org https://cache.iog.io
trusted-public-keys = hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ= cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
</code></pre>
<p>then you should have the binary cache from IOG working again.
(you many need to log out and log back in and or restart the nix daemon to get these changes to take)</p>
<p><a href="https://github.com/input-output-hk/cardano-node/blob/master/doc/getting-started/building-the-node-using-nix.md#iohk-binary-cache" rel="nofollow noreferrer">Doc source</a></p>
