Hi @janrik – Twenty Twenty-Three is a block theme and does not support widgets.
This plugin is only for use on classic themes (which support widgets) such as Twenty Twenty-One:
Once activated and when using a classic (non-block) theme, this plugin restores the previous widgets settings screens and disables the block editor from managing widgets.
In a block theme like Twenty Twenty-Three, you can add content via the Site Editor. For a better understanding of block themes and TT3 in particular, check out the resources here:
https://www.ads-software.com/support/topic/support-resources-for-twenty-twenty-three/
Let me know if you have other questions!