Thanks for the pointer. Just tried it here, to no avail. Found some error messages in logs, though:
Message
TypeError: Discourse.Route is undefined
Url: https://rede.tropixel.org/assets/plugins/discourse-rss-poster-0aabbb3898d14427e95a811b6122e396e4df614f63b9abc852500d40eebac63e.js
Line: 1
Column: 4457
Window Location: https://rede.tropixel.org/admin/plugins/chat/matrix
Backtrace
@https://rede.tropixel.org/assets/plugins/discourse-rss-poster-0aabbb3898d14427e95a811b6122e396e4df614f63b9abc852500d40eebac63e.js:1:4457
require/<@https://rede.tropixel.org/assets/ember_jquery-1ed3f3559e6f967733b4088aa729ff7039dff2c09c5a5f787a214b016f58aabc.js:1:562030
require/<@https://rede.tropixel.org/assets/ember_jquery-1ed3f3559e6f967733b4088aa729ff7039dff2c09c5a5f787a214b016f58aabc.js:1:561743
require@https://rede.tropixel.org/assets/ember_jquery-1ed3f3559e6f967733b4088aa729ff7039dff2c09c5a5f787a214b016f58aabc.js:1:561760
customResolve@https://rede.tropixel.org/assets/application-46046b7ac1724a22e8df0ccd326808196b37590a888951a9755a8fefb8c98aef.js:1:19092
resolveRoute@https://rede.tropixel.org/assets/application-46046b7ac1724a22e8df0ccd326808196b37590a888951a9755a8fefb8c98aef.js:1:19899
e@https://rede.tropixel.org/assets/ember_jquery-1ed3f3559e6f967733b4088aa729ff7039dff2c09c5a5f787a214b016f58aabc.js:1:297670
a</n.resolve@https://rede.tropixel.org/assets/ember_jquery-1ed3f3559e6f967733b4088aa729ff7039dff2c09c5a5f787a214b016f58aabc.js:1:322415
g</t.resolve/r<@https://rede.tropixel.org/assets/ember_jquery-1ed3f3559e6f967733b4088aa729ff7039dff2c09c5a5f787a214b016f58aabc.js:1:96972
g</t.resolve@https://rede.tropixel.org/assets/ember_jquery-1ed3f3559e6f967733b4088aa729ff7039dff2c09c5a5f787a214b016f58aabc.js:1:97078
Env
HTTP HOSTS: rede.tropixel.org