This is because of our defaults, we are using by default OpenSSL. I am aware that OpenWrt defaults are mbedTLS due to space limitations, most importantly that there was lack of support in hostapd, but they will be using wolfSSL in OpenWrt 21.02.
I agree with you that we should update or document it more. BFU can be confused when he received the message - package is missing. Did I do smth wrong or what should I do? Because of that, I created a few issues to create articles or improve our current documentation. It can be seen here https://gitlab.nic.cz/turris/user-docs/-/issues