Hello Louise Philippe Earnshaw,
Thank you for posting in Q&A forum.
I understand you want to install RSAT, you can try another two ways in the link below, there are detailed steps for your reference.
https://www.prajwaldesai.com/how-to-install-rsat-on-windows-11/
Similar thread for your reference.
https://techcommunity.microsoft.com/t5/windows-11/how-to-install-or-uninstall-rsat-in-windows-11/m-p/3273590
I hope the information above is helpful.
If you have any questions or concerns, please feel free to let us know.
Best Regards,
Daisy Zhou
============================================
If the Answer is helpful, please click "Accept Answer" and upvote it.