Ok I’m a step further now, didn’t notice you have to upload the minified source too. Added the bundle.js and now I get an Invalid location in sourcemap error.
However, all browsers and source-map-visualization are able to find the exact place sentry reports in the sourcemap and correctly display the according code.
I tried a lot of things over the course of the last days, including:
Setting a whole new project
Creating a minimal reproduction project with sentry + 1 line of code
Up/Downgrading typescript/webpack in all combinations
Tried a lot of different webpack configs
All other tools / browsers are able to read the sourcemap, but sentry consistently refuses to do so.