While during development everything works fine, the final app (more specifically, the created app.asar) does not contain any resources such as the fonts or the feather icon.
Build the current develop branch using yarn package and open the resulting App/Exe/Binary. The developer tools will then tell you:

Package the assets (or, if the assets are packaged, fix the paths)
Pinging @tobiasdiez: Do you know what the issue could be?
Looks like the following: https://github.com/electron-userland/electron-forge/issues/1196
Thanks, I will have a look! :) If you manage to implement this quickly, please go forward!
I'm currently traveling, so sadly no access to a dev-setup.
Easy, I'll try to spin up an early alpha on Friday so that we can begin gradually testing everything out … no hurry here.
And fixed — the issue was precisely what went wrong! Thanks for the research.
Glad it worked!
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And fixed — the issue was precisely what went wrong! Thanks for the research.