$ tce-load -i compiletc perl5 bash ncursesw-dev bc glibc_apps elfutils-dev git
$ cd $HOME/Downloads
$ git clone https://git.zx2c4.com/wireguard-linux-compat
$ wget http://tinycorelinux.net/11.x/x86_64/release/src/kernel/linux-5.4.3-patched.txz
$ wget http://tinycorelinux.net/11.x/x86_64/release/src/kernel/config-5.4.3-tinycore64
$ tar -xvf linux-5.4.3-patched.txz
$ cd linux-5.4.3
$ cp ../config-5.4.3-tinycore .config
$ ../wireguard-linux-compat/kernel-tree-scripts/jury-rig.sh $HOME/Downloads/linux-5.4.3
$ make oldconfig
-> when asked about CONFIG_WIREGUARD choose M, when asked about CONFIG_WIREGUARD_DEBUG choose as you like (I went with y)
$ make prepare scripts
$ make M=net/wireguard modules
-> payload (the kernel module) is $HOME/Downloads/linux-5.4.3/net/wireguard/wireguard.ko