Adding OARS,

changing the metadata license to CC0-1 (as required by Flathub),
Corrected Typo in appdata,
Removing unnecessary permissions

sh.popcorntime.PopcornTime.appdata.xml

@@ -2,9 +2,9 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <component type="desktop">
   <id>sh.popcorntime.PopcornTime.desktop</id>
-  <metadata_license>GFDL-1.3</metadata_license>
+  <metadata_license>CC0-1.0</metadata_license>
   <project_license>GPL-3.0</project_license>
-  <name>PopcornTimer</name>
+  <name>PopcornTime</name>
   <summary>Watch Movies and TV Shows instantly</summary>
   ​<translation type="gettext">PopcornTime</translation>
   <update_contact>preisschild_AT_protonmail.com</update_contact>
@@ -15,6 +15,28 @@
         Popcorn Time uses sequential downloading to stream video listed by several torrent websites, and third party trackers can also be added manually.
     </p>
   </description>
+  <content_rating type="oars-1.1">
+    <content_attribute id="violence-cartoon">moderate</content_attribute>
+    <content_attribute id="violence-fantasy">moderate</content_attribute>
+    <content_attribute id="violence-realistic">moderate</content_attribute>
+    <content_attribute id="violence-bloodshed">moderate</content_attribute>
+    <content_attribute id="violence-sexual">moderate</content_attribute>
+    <content_attribute id="violence-desecration">moderate</content_attribute>
+    <content_attribute id="violence-slavery">moderate</content_attribute>
+    <content_attribute id="violence-worship">moderate</content_attribute>
+    <content_attribute id="drugs-alcohol">moderate</content_attribute>
+    <content_attribute id="drugs-narcotics">moderate</content_attribute>
+    <content_attribute id="drugs-tobacco">moderate</content_attribute>
+    <content_attribute id="sex-nudity">moderate</content_attribute>
+    <content_attribute id="sex-themes">moderate</content_attribute>
+    <content_attribute id="sex-homosexuality">moderate</content_attribute>
+    <content_attribute id="sex-prostitution">moderate</content_attribute>
+    <content_attribute id="sex-adultery">moderate</content_attribute>
+    <content_attribute id="sex-appearance">moderate</content_attribute>
+    <content_attribute id="language-profanity">moderate</content_attribute>
+    <content_attribute id="language-humor">moderate</content_attribute>
+    <content_attribute id="language-discrimination">moderate</content_attribute>
+  </content_rating>
   <url type="homepage">https://popcorntime.sh/</url>
   <screenshots>
     <screenshot type="default">https://i.imgur.com/UtKMSso.jpg</screenshot>

sh.popcorntime.PopcornTime.yml

@@ -10,10 +10,9 @@ separate-locales: false
 finish-args:
 - --share=ipc
 - --share=network
-- --device=all
 - --socket=x11
 - --socket=pulseaudio
-- --filesystem=home
+- --filesystem=home:ro
 - --talk-name=org.freedesktop.Notifications
 modules:
 - shared-modules/gtk2/gtk2.json