Wireguard package is available in opkg repo and may be installed without any errors in terminal.
But kernel module (wireguard.ko from package kmod-wireguard) seems to be broken so the interface wg0 keeps uninitialised.
Loaded by hands wireguard.ko produces no warning but still stays unloaded. lsmod | grep wireguard finds nothing.
In logread these lines were added:
daemon.notice netifd: Interface ‘wg0’ is now down
daemon.notice netifd: Interface ‘wg0’ is setting up now
daemon.notice netifd: wg0 (16051): Error: Unknown device type.
daemon.notice netifd: wg0 (16051): Unable to modify interface: Protocol not supported