In macOS 11 and later, the kernel doesn’t load a kext if an equivalent System Extension solution exists. You may continue to use kexts in macOS 10.15 and earlier to support those devices / services.
See:
https://developer.apple.com/documentation/kernel/implementing_drivers_system_extensions_and_kextsmacOS 11 will continue to link and load kexts that have no System Extension solution available. There are, however, additional restrictions on kexts in macOS 11. A reboot will be required whenever a kext is installed or updated, and the user must approve each update to the kext in the System Preferences Security pane.
Apple silicon macs will support kernel extensions with similar restrictions.