Thunderbird fails to display SVG and doesn't indicate with broken image icon/alt-text

Checklist

• I have used the search function to see if someone else has already submitted the same bug report.
• I will describe the problem with as much detail as possible.

App

Thunderbird for Android

App version

12.1

Where did you get the app from?

F-Droid

Android version

14

Device model

No response

Steps to reproduce

1. broken image icon: Add inline SVG to email for eg. using thunderbird desktop with insert as html add the <svg>...</svg> code. You can also try with role="img" attribute.

2. Alt text: add <svg>...<title> Alt text here </title></svg> to add alt text in case client can't render svg. This format is common and used by MathJax, for example, so you can find such svg in email with LaTeX prerendered using MathJax SVG. Alternatively try some garbage tag <svg>...<afindgnweiu> Alt text here </afindgnweiu></svg> or even <desc>.

Expected behavior

Show image broken/missing icon in place and show the <title> of the svg which works on desktop and everywhere else. <desc> and garbage tags are shown as alt-text but not <title> which is more commonly used.

see info on SVG title/Desc spec: mdn article on title, mdn article on desc
see tangentially related issue #3412

Actual behavior

Renders properly on desktop and roundcube webmail, etc. and shows broken icon/alt-text when display-as is changed on desktop as expected but thunderbird android doesn't render this but also doesn't show an image missing/broken icon or alt text either. Thunderbird android does show broken image and alt text for remote svg content in img tag but not embedded svg.

Logs

No response

Start by reproducing the issue in Thunderbird for Android 12.1 with an inline SVG containing a title, desc, or invalid child tag, then trace the email rendering path. Done means unsupported or failed inline SVG content shows a broken-image indicator and exposes the SVG title as alt text, matching the reported desktop behavior.