How do you use USB passthrough? After a lot of troubleshooting I’ve pinpointed the RAM limit patch to not work with stubdom-qrexec feature. From package xen-hvm-stubdom-linux-full. It’s detailed in this post.
Just Qubes Windows Tools won’t let me USB passthrough.
Edit: Thanks to @jevank I learned I need to patch qemu-stubdom-linux-full-rootfs after installing xen-hvm-stubdom-linux-full. Working now.