<p>I had some trouble in the past too. </p>

<p>Now the solution I use is this <a href="https://github.com/sprig/org-capture-extension" rel="nofollow noreferrer">firefox add-on</a> -> You can install it directly from Firefox. That's really easy and in my case, it worked out of the box (Debian distro, Firefox 52.5.0). I do not know if it is available for Firefox Quantum though. </p>

<p><a href="http://orgmode.org/worg/org-contrib/org-protocol.html" rel="nofollow noreferrer">org-protocol</a> is configured as usual. In my case:</p>

<pre><code>cat &gt; "${HOME}/.local/share/applications/org-protocol.desktop" &lt;&lt; EOF
[Desktop Entry]
Name=org-protocol
Exec=emacsclient %u
Type=Application
Terminal=false
Categories=System;
MimeType=x-scheme-handler/org-protocol;
EOF
</code></pre>

<p>then</p>

<pre><code>update-desktop-database ~/.local/share/applications/
</code></pre>

<p>In your Emacs <code>init.el</code> file:</p>

<pre><code>(server-start)
(require 'org-protocol)

(setq org-capture-templates `(
    ("p" "Protocol" entry (file+headline ,(concat org-directory "notes.org") "Inbox")
        "* %^{Title}\nSource: %u, %c\n #+BEGIN_QUOTE\n%i\n#+END_QUOTE\n\n\n%?")
    ("L" "Protocol Link" entry (file+headline ,(concat org-directory "notes.org") "Inbox")
        "* %? [[%:link][%:description]] \nCaptured On: %U")
))
</code></pre>

<p>That's all. Under my config it works, I hope this is the same for yours.</p>

<hr>

<p><strong>Extra:</strong> some time ago, I have suggested a small template improvement to handle ArXiv.org titles, the details are here: <a href="https://github.com/sprig/org-capture-extension/issues/37" rel="nofollow noreferrer">https://github.com/sprig/org-capture-extension/issues/37</a></p>
getting org-protocol to work on Firefox Quantum -- `No server buffers remain to edit` error
<p>So I am trying to get <code>org-protocol</code> to work for the first time on Firefox Quantum. I worked through a variety of blog posts and the documentation, but still cannot get past this particular error </p>

<pre><code>Greedy org-protocol handler.  Killing client. 
No server buffers remain to edit.
</code></pre>

<p>So I am using emacs 25.3 on Ubuntu Linux x64 16.04, and the newly released Firefox Quantum. </p>

<p>I tried to do this in two ways. </p>

<ol>
<li><p>The traditional approach of setting up <code>org-protocol</code> through creating a desktop entry and then setting up bookmarklets in Firefox. </p></li>
<li><p>Using the <code>org-capture</code> add-on in Firefox. </p></li>
</ol>

<p>Both are giving me the same error. </p>

<p>For approach 1, I followed the <a href="http://orgmode.org/worg/org-contrib/org-protocol.html#sec-6-1" rel="nofollow noreferrer">documentation</a> as well as a very helpful stackexchange post:</p>

<p><a href="https://stackoverflow.com/questions/7464951/how-to-make-org-protocol-work">How to make org-protocol work?</a> </p>

<p>There was also this useful blog <a href="http://www.mediaonfire.com/blog/2017_07_21_org_protocol_firefox.html" rel="nofollow noreferrer">post</a>.</p>

<p>Here is what I did:</p>

<p>A. I created a desktop entry:</p>

<pre><code>[Desktop Entry]
Name=org-protocol
Exec=emacsclient -n %u
Type=Application
Terminal=false
Categories=System;
MimeType=x-scheme-handler/org-protocol;
</code></pre>

<p>B. added config to <code>.spacemacs</code> file.</p>

<p>I added the lines:</p>

<pre><code>(server-start)
(require 'org-protocol)
</code></pre>

<p>Then I setup up the capture template in my <code>.spacemacs</code> file:</p>

<pre><code>(setq org-capture-templates
      (quote 
              ("p" "org-protocol" entry (file+headline "~/Dropbox/config/org/refile/refile.org")
                "* %^{Title}\nSource: %u, %c\n #+BEGIN_QUOTE\n%:initial\n#+END_QUOTE\n\n\n%?")
              ("l" "org-protocol link" entry (file "~/Dropbox/config/org/refile/refile.org")
                "* %? [[%:link][%:description]] \nCaptured On: %U")
... Additional templates.
))
</code></pre>

<p>C. Then I created the bookmarklets with the locations:</p>

<pre><code>javascript:location.href='org-protocol://store-link://l/'+encodeURIComponent(location.href)

javascript:location.href='org-protocol://capture://l/'+encodeURIComponent(location.href)+'/'+encodeURIComponent(document.title)+'/'+encodeURIComponent(window.getSelection())
</code></pre>

<p>After all of this, I still get the error message referenced above. </p>

<p>Second, I tried the <code>org-capture</code> add-on in Firefox. But it did not work either. </p>

<p>Not sure what the cause of the error is. Any help is appreciated.</p>

<p>In other reading people get this <code>Greedy</code> error when there are problems in the <code>org-capture</code> template, but I did not find any errors.  </p>