You will see the "style" section is different. Mine allows unsafe-inline, yours allows only a single nonce
You need to make it return the correct thing. You can also check the console logs in the browser to see the errors resulting from this.
Paste your Nginx file into ChatGPT and ask how to do it.
I don't want to write up specific instructions on this because I don't want to encourage other people to do it. It's not a good thing. Akkoma has broken support for other frontends. This is an Akkoma problem.
@alan@burner Did you see my reply to them? They are not using Soapbox as the main frontend. This is what I mean by "Soapbox supports Akkoma, but Akkoma does not support Soapbox." In their custom setup the are running Soapbox atop Akkoma with a custom Nginx to control headers and routing. They have made it work with a custom setup. The default setup is the opposite, where Akkoma is in front and Soapbox is served through it, so Akkoma controls it.
There is no easy way out of this. You're going to have to read up and learn how this all works.