BSDs are also monolithic kernels, just like Linux, macOS, and Windows NT

FreeBSD has been trying to make it easier to run as a desktop OS by supporting the Linux APIs so they can use the WiFi and Graphics drivers from Linux

OpenBSD handles security by supporting fewer features. E.g. they do not support Bluetooth as it’s an insecure protocol, and they disabled SMT due to the hardware bugs in AMD/Intel/ARM - so they are more secure, but slower