Try using verbatim filter

submissions/templates/submissions/_report_tex_template.html

@@ -34,7 +34,7 @@
 \Large\color{scipostdeepblue}{\textbf{
 %%%%%%%%%% TITLE
 Report nr {{report.report_nr}} on Submission {{ report.submission.arxiv_identifier_w_vn_nr }},\\
-\href{https://scipost.org{{report.submission.get_absolute_url|safe_tex_url}} }{\color{scipostdeepblue}{ {{report.submission.title}} }}by {{report.submission.author_list}}
+\href{https://scipost.org{{report.submission.get_absolute_url|safe_tex_url}}}{\color{scipostdeepblue}{ {{report.submission.title}} }}by {{report.submission.author_list}}
 }}
 \end{center}
 
@@ -72,7 +72,7 @@ Published by the SciPost Foundation.
 %%%%%%%%%% DATES
 {\small Received {{report.date_submitted|date:'d-m-Y'}}
 {% if report.doi_string %}
-    \doi{ {{report.doi_string|safe_tex_url}} }
+{% verbatim %}\doi{{% endverbatim %}{{report.doi_string|safe_tex_url}}}
 {% endif %}
 }
 \end{minipage}