Hi, micha_800!
Thanks for reaching Microsoft Community. We are sorry to learn that you encounter an error when trying to install the Citrix Gateway Plug-in on your Surface Pro X. This happens if the software is not compatible. Kindly check this page to view an article about the Surface Pro X app compatibility to learn more how installation works with apps on the device.
64-bit (x64) apps won’t work. You'll need 64-bit (ARM64) apps, 32-bit (ARM32) apps, or 32-bit (x86) apps. You can usually find 32-bit (x86) versions of apps, but some app developers only offer 64-bit (x64) apps.
I managed to check the Citrix website and encountered this page that mentions the Citrix Gateway plug-in System Requirements. It mentions there that it supports the Windows 10 (x86 and x64) Operating System.
Kindly check with the developer of the Citrix Gateway Plug-in if they are working on the availability for the ARM architecture so ARM-based PCs will work with their software.
We hope this helps you out, we highly encourage you to inform our Community by clicking on Yes or marking my post as an answer. This will help other members who may have the same issue as you. Otherwise, don't hesitate to update us so we can further assist you.
Kind regards,
Janette_Z