QtWebEngine does not adhere to the OS/DE fonts.

As bugs.kde.org/show_bug.cgi?id=496012 explains:

Unable to find source-code formatter for language: markdown. Available languages are: actionscript, ada, applescript, bash, c, c#, c++, cpp, css, erlang, go, groovy, haskell, html, java, javascript, js, json, lua, none, nyan, objc, perl, php, python, r, rainbow, ruby, scala, sh, sql, swift, visualbasic, xml, yaml

SUMMARY
-------

My `kcm_fonts` font preferences are not applied to Web Browser's embedded Chromium instance.

[STEPS TO REPRODUCE][7]
-----------------------

1. Add the Web Browser plasmoid to the `plasmashell` desktop.
2. Render any HTML file (at any URI) that doesn't explicitly define a font.

OBSERVED RESULT
---------------

My `kcm_fonts` font preferences are not applied to the embedded Chromium instance.

EXPECTED RESULT
---------------

They should be.

[SOFTWARE/OS VERSIONS][2]
-------------------------

1. ~~~sh
   #!/usr/bin/env -S bash
   kinfo
   ~~~

2. > ~~~YAML
   > Operating System       : Fedora Linux 41
   > KDE Plasma Version     : 6.2.4
   > KDE Frameworks Version : 6.8.0
   > Qt Version             : 6.8.0
   > Kernel Version         : 6.11.10-300.fc41.x86_64 (64-bit)
   > Graphics Platform      : Wayland
   > Processors             : 12 × AMD Ryzen 5 7600X 6-Core Processor
   > Memory                 : 30.4 GiB of RAM
   > Graphics Processor     : AMD Radeon RX 5700
   > Manufacturer           : ASRock
   > Product Name           : X670E Taichi
   > ~~~

ADDITIONAL INFORMATION
----------------------

I have filed a similar ticket for the *icons* upstream — at https://issues.chromium.org/issues/378121132#comment1. I didn't consider that to be worth reporting here.

This ticket differs to that, because the font fallbacks are an unfortunate consequence of backward compatibility which Google has no desire to remediate.

Jira's formatting system doesn't appear to be equipped to handle vaguely advanced formatting, but I'll try to convert it.