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Unexpected token < in JSON when trying to load a panel

See original GitHub issue

Migrating from django-debug-toolbar from 2.2 to 3.1.1 Django version: 3.1.1

When clicking onto a panel, the loading indicator runs forever due to an error in a JS promise. The issue seems to be attempting to parse an HTML document as JSON. I have verified that the latest mime-support package is installed on my Ubuntu container per https://django-debug-toolbar.readthedocs.io/en/latest/installation.html#troubleshooting and the other prerequisites should be complete.

https://github.com/jazzband/django-debug-toolbar/blob/master/debug_toolbar/static/debug_toolbar/js/toolbar.js#L43 The request is to /__debug__/render_panel/?store_id=...&panel_id=SQLPanel

The failing JSON parse is: https://github.com/jazzband/django-debug-toolbar/blob/master/debug_toolbar/static/debug_toolbar/js/utils.js#L42

Setting a breakpoint at return response.json(); and manually getting the value in the console:

response.text().then(function (text) {
  console.log(text);
});

I do get an HTML document beginning like this, which appears to be a JSON document rendered in an HTML page:

<html><body><pre>{
  "content": "\n<ul>\n  \n    <li>\n      <strong><span class=\"djdt-color\" style=\"background-color:rgb(256, 0, 0)\"></span> default</strong>\n      0.94 ms (3 queries\n      \n        including <abbr title=\"Similar queries are queries with the same SQL, but potentially different parameters.\">2 similar</abbr>\n        \n          and <abbr title=\"Duplicate queries are identical to each other: they execute exactly the same SQL and parameters.\">2 duplicates</abbr>\n        \n      )\n    </li>\n  \n</ul>\n\n\n  <table>\n    <thead>\n      <tr>\n        <th></th>\n        <th class=\"djdt-query\" colspan=\"2\">Query</th>\n        <th class=\"djdt-timeline\">Timeline</th>\n        <th class=\"djdt-time\">Time (ms)</th>\n

The opening left bracket from <html> is what leads to the error Uncaught (in promise) SyntaxError: Unexpected token < in JSON at position 0 from what I gather.