You’ll find the 32-bit Version on GitHub Releases · nextcloud/desktop · GitHub
It works fine with my Windows 10 on ARM (Surface Pro X).
I hope NextCloud compile the NextCloud-Client for ARM64 too soon. In my understanding it should just be an enabling an additional compile option in Visual Studio, or was at my times as active programmer.
Any additional ARM-Adaptions in source code must be made anyway for Macs on ARM.