Convert your key to dropbear key

wget https://matt.ucc.asn.au/dropbear/releases/dropbear-2022.82.tar.bz2

tar -xf dropbear-2022.82.tar.bz2

cd ./dropbear-2022.82/

./configure

make PROGRAMS=”dropbear dbclient dropbearkey dropbearconvert scp”

The result is make error.
It doesn’t matter because dropbearconvert is ready.

Now, you can prepare key(id_rsa).
dropbear-2022.82/dropbearconvert openssh dropbear id_rsa id_dropbear