Please update jami-gnome.appdata.xml to show screenshots etc. Hopefully this will be propagated to:
https://flathub.org/apps/details/net.jami.Jami
Unfortunately, could not update the text directly so the suggested text is shown below:
<?xml version="1.0" encoding="UTF-8"?>
<!-- Copyright 2009-2018 Savoir-faire Linux -->
<!-- https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html -->
<component type="desktop">
<id>gnome-ring.desktop</id>
<metadata_license>CC-BY-SA-3.0</metadata_license>
<name>Jami</name>
<summary>Secure and distributed communication and SIP client</summary>
<description>
<p>
Jami is a secure and distributed file transfer, voice, video and chat communication platform
that requires no centralized server and leaves the power of privacy in the hands of the user.
</p>
<p>
Jami also includes a SIP client.
</p>
<p>
Jami is free software which allows its users to communicate in multiple ways.
</p>
<ul>
<li>A telephone: a simple tool to connect, communicate and share.</li>
<li>A teleconferencing tool: easily join calls to create conferences with multiple
participants.</li>
<li>A media sharing tool: Jami supports a variety of video input options, including
multiple cameras and image and video files, and the selection of audio inputs
and outputs; all this is supported by multiple high quality audio and video
codecs.</li>
<li>A messenger: send text messages during calls or out of calls (as long as your
peer is connected).</li>
<li>A building block for your IoT project: re-use the universal communications
technology of Jami with its portable library on your system of choice.</li>
<ul>
<p>
Jami is also available on Microsoft Windows, Apple macOS, Apple iOS and Google Android.
</p>
<p>
Jami a free and open-source cross-platform universal communication platform
developed by a team at Savoir-faire Linux and a growing community of contributors.
To to contribute, visit https://jami.net/contribute/
</p>
<p>
Jami was based on GNU Ring (formerly SFLphone).
</p>
</description>
<!-- https://specifications.freedesktop.org/menu-spec/latest/apa.html -->
<!-- https://specifications.freedesktop.org/menu-spec/latest/apas02.html -->
<categories>
<category>Chat</category>
<category>Communication</category>
<category>InstantMessaging</category>
<category>Office</category>
<category>Productivity</category>
</categories>
<url type="homepage">https://jami.net/</url>
<url type="bugtracker">https://jami.net/bugs-and-improvements/</url>
<url type="faq">https://jami.net/help/</url>
<url type="help">https://git.ring.cx/savoirfairelinux/ring-project/wikis/home</url>
<url type="donation">https://jami.net/business-customization/</url>
<url type="translate">https://www.transifex.com/savoirfairelinux/jami/</url>
<launchable type="desktop-id">net.jami.Jami.desktop</launchable>
<!-- https://www.unixtimestamp.com/index.php -->
<releases>
<release version="2.0" date="2019-03-19" urgency="high" />
<description>
<p>This stable release fixes bugs.</p>
</description>
</releases>
<!-- A GNU package -->
<project_group>GNU</project_group>
<project_license>GPL-3.0+</project_license>
<developer_name>Savoir-faire Linux</developer_name>
<!--
From the official Jami website
https://jami.net/
-->
<screenshots>
<screenshot type="default">
<caption>Make audio calls between Jami users with 48 kHz audio quality.</caption>
<image type="remote"
width="600"
height="400">
https://jami.net/assets/images/audio-call.gif
</image>
</screenshot>
<screenshot>
<caption>Enjoy conference calls with an unlimited number of participants with crystal clear Opus audio quality of 48 kHz.</caption>
<image type="remote"
width="600"
height="400">
https://jami.net/assets/images/conference.gif
</image>
</screenshot>
<screenshot>
<caption>Experience HD video calls.</caption>
<image type="remote"
width="600"
height="400">
https://jami.net/assets/images/video-call.gif
</image>
</screenshot>
<screenshot>
<caption>Benefit from encrypted and secure text messaging, without any central server, utilizing a distributed network.</caption>
<image type="remote"
width="600"
height="400">
https://jami.net/assets/images/chat.gif
</image>
</screenshot>
<screenshot>
<caption>Share expressions and emotions using emoji and GIF punctuation.</caption>
<image type="remote"
width="600"
height="400">
https://jami.net/assets/images/emoji.png
</image>
</screenshot>
<screenshot>
<caption>Record your voice in one click. Useful when you have a long story to tell.</caption>
<image type="remote"
width="600"
height="400">
https://jami.net/assets/images/vocal-share.gif
</image>
</screenshot>
<screenshot>
<caption>It is possible to record video messages and send them to Jami users.</caption>
<image type="remote"
width="600"
height="400">
https://jami.net/assets/images/video-share.gif
</image>
</screenshot>
<screenshot>
<caption>Share photos of unforgettable moments.</caption>
<image type="remote"
width="600"
height="400">
https://jami.net/assets/images/pictures-share.gif
</image>
</screenshot>
<screenshot>
<caption>Send files of all sizes between Jami users. Automatically download files with flac, gif, jpeg, jpg, mkv, mp3, mp4, ogg, png, wav, webm and webp filename extensions.</caption>
<image type="remote"
width="600"
height="400">
https://jami.net/assets/images/files-share.gif
</image>
</screenshot>
</screenshots>
<update_contact>adrien.beraud@savoirfairelinux.com</update_contact>
<suggests>
<id>org.libreoffice.LibreOffice</id>
</suggests>
<content_rating type="oars-1.0">
<content_attribute id="violence-cartoon">none</content_attribute>
<content_attribute id="violence-fantasy">none</content_attribute>
<content_attribute id="violence-realistic">none</content_attribute>
<content_attribute id="violence-bloodshed">none</content_attribute>
<content_attribute id="violence-sexual">none</content_attribute>
<content_attribute id="drugs-alcohol">none</content_attribute>
<content_attribute id="drugs-narcotics">none</content_attribute>
<content_attribute id="drugs-tobacco">none</content_attribute>
<content_attribute id="sex-nudity">none</content_attribute>
<content_attribute id="sex-themes">none</content_attribute>
<content_attribute id="language-profanity">none</content_attribute>
<content_attribute id="language-humor">none</content_attribute>
<content_attribute id="language-discrimination">none</content_attribute>
<content_attribute id="social-chat">intense</content_attribute>
<content_attribute id="social-info">intense</content_attribute>
<content_attribute id="social-audio">none</content_attribute>
<content_attribute id="social-location">none</content_attribute>
<content_attribute id="social-contacts">none</content_attribute>
<content_attribute id="money-purchasing">none</content_attribute>
<content_attribute id="money-gambling">none</content_attribute>
</content_rating>
</component>