Error when accessing wiki.xfce.org using older Chromium-based browsers

First off, apologies if this is not the right place to post this kind of issue. Please point me to a proper avenue to report this bug. Thanks :)

These domains:

• wiki.xfce.org
• gitlab.xfce.org
• docs.xfce.org

All cannot be accessed by older Chromium-based browsers (versions lower than 140). I had to use a User-Agent spoofer to even be able to post this issue.

I have confirmed that Chromium-based browsers with versions less than 140 don't work. For example, on my browser Thorium 138, I get the error ERR_HTTP2_PROTOCOL_ERROR when I tried to open https://gitlab.xfce.org/

Firefox works.

This problem can be reproduced in the command line using curl. This is the minimal command:

curl -v --http2 -A 'Mozilla/5.0 Chrome/138.0.0.0' 'https://gitlab.xfce.org/'

Even HTTP 1.1 doesn't work:

curl -v --http1.1 -A 'Mozilla/5.0 Chrome/138.0.0.0' 'https://gitlab.xfce.org/'

I tried versions 140, 143, 148, 150, even 160 and 180 (the last two being fictional), all of these worked. I tried versions 139, 138, 130, 120, 110, 100, and 30, all of these didn't work.

Minimum versions for other xfce.org domains:

• blog.xfce.org needs version 137
• forum.xfce.org no minimum version
• archive.xfce.org no minimum version
• cdn.xfce.org no minimum version
• www.xfce.org no minimum version
• xfce.org no minimum version