Wifislax 3.2 uses an older Xorg. Boot with nomodeset from the boot menu (press Tab, add nomodeset ).
For real Wi-Fi auditing, you need a USB Wi-Fi adapter passed through to the VM – but this is cumbersome and often fails with legacy version 3.2 on modern hypervisors. Stick to Live USB. wifislax 3.2 download
slackpkg install compat32