Try to get GNOME Software entry of Briar working

briar-gtk/data/app.briar.gtk.desktop.in

 [Desktop Entry]
+Version=1.0
 Name=Briar
-Comment=Secure messaging, anywhere
-Keywords=Briar;
+Keywords=chat;talk;im;message;briar;tor;
+Exec=briar-gtk %U
 Icon=app.briar.gtk
-Exec=briar-gtk
+StartupNotify=false
 Terminal=false
 Type=Application
-Categories=GNOME;GTK;
-StartupNotify=true
+Categories=GTK;Network;Chat;InstantMessaging;
+X-GNOME-UsesNotifications=true

briar-gtk/data/app.briar.gtk.appdata.xml.in → briar-gtk/data/app.briar.gtk.metainfo.xml.in

 <?xml version="1.0" encoding="UTF-8"?>
+<!-- Copyright 2020 Nico Alt <nicoalt@posteo.org> -->
 <component type="desktop-application">
   <id>app.briar.gtk</id>
   <metadata_license>CC-BY-4.0</metadata_license>
@@ -57,6 +58,10 @@
     <content_attribute id="social-chat">intense</content_attribute>
   </content_rating>
 
+  <provides>
+    <binary>briar-gtk</binary>
+  </provides>
+
   <releases>
     <release version="0.1.0-alpha1" date="2020-04-12">
       <description>

briar-gtk/data/meson.build

@@ -19,8 +19,8 @@ if desktop_utils.found()
 endif
 
 appstream_file = i18n.merge_file(
-  input: 'app.briar.gtk.appdata.xml.in',
-  output: 'app.briar.gtk.appdata.xml',
+  input: 'app.briar.gtk.metainfo.xml.in',
+  output: 'app.briar.gtk.metainfo.xml',
   po_dir: '../po',
   install: true,
   install_dir: join_paths(get_option('datadir'), 'metainfo')