No response when running behind a proxy

[Wend1go]

Starting superpowers-app from behind a proxy makes the UI unresponsive. Clicking buttons for settings or starting the server has no effect.
It would be nice if the app could run locally without network access.

Console output:
Loading settings from /home/xxxx/.config/Superpowers/settings.json. api.github.com/repos/superpowers/superpowers-app/releases/latest Failed to load resource: net::ERR_PROXY_CONNECTION_FAILED /home/xxxx/development/superpowers-v5.2.0-linux-x64/resources/app/shared/fetch.js:15 ProgressEvent superpowers-html5.com/news.de.html Failed to load resource: net::ERR_PROXY_CONNECTION_FAILED /home/xxxx/development/superpowers-v5.2.0-linux-x64/resources/app/shared/fetch.js:15 ProgressEvent superpowers-html5.com/news.en.html Failed to load resource: net::ERR_PROXY_CONNECTION_FAILED /home/xxxx/development/superpowers-v5.2.0-linux-x64/resources/app/shared/fetch.js:15 ProgressEvent superpowers-html5.com/news.en.html Failed to load resource: net::ERR_PROXY_CONNECTION_FAILED /home/xxxx/development/superpowers-v5.2.0-linux-x64/resources/app/shared/fetch.js:15 ProgressEvent