CONFIG_TCP_MD5SIG not enabled anymore on 21.02 but breaks packages

Ahoy ahoy friends.
I have been using a OpenWrt system with BGP from the master branch for a long time.
Now i have moved to the stable branch, but it breaks my BGP connections, it was difficult to troubleshoot.
The reason for that is: CONFIG_TCP_MD5SIG seems to be disabled by default now in the .kconfig in case of OpenWrt 21.02. Unfortunately MD5 authentication in BGP doesn't work anymore which is provided by quagga and frr, and it is extremely difficult to troubleshoot.

./tmp/.kconfig-x86_64:6225:# CONFIG_TCP_MD5SIG is not set

How to fix this issue? I am unable to use make kernel_menuconfig in order to enable that.
Also i think it should be a dependency for the packages quagga and frr, because after an upgrade, i think some people might suffer this issue as well, without knowing what's wrong.

The result are malformed TCP packets, and this log in the bgpd daemon.

2021/09/24 12:49:16 BGP: can't set TCP_MD5SIG option on socket 13: Protocol not available
2021/09/24 12:49:20 BGP: sockopt_tcp_signature: setsockopt(12): Protocol not available
2021/09/24 12:49:20 BGP: can't set TCP_MD5SIG option on socket 12: Protocol not available
2021/09/24 12:49:21 BGP: sockopt_tcp_signature: setsockopt(13): Protocol not available
2021/09/24 12:49:21 BGP: can't set TCP_MD5SIG option on socket 13: Protocol not available
2021/09/24 12:49:25 BGP: sockopt_tcp_signature: setsockopt(12): Protocol not available
2021/09/24 12:49:25 BGP: can't set TCP_MD5SIG option on socket 12: Protocol not available
2021/09/24 12:49:26 BGP: sockopt_tcp_signature: setsockopt(13): Protocol not available
2021/09/24 12:49:26 BGP: can't set TCP_MD5SIG option on socket 13: Protocol not available
2021/09/24 12:49:30 BGP: sockopt_tcp_signature: setsockopt(12): Protocol not available
2021/09/24 12:49:30 BGP: can't set TCP_MD5SIG option on socket 12: Protocol not available
2021/09/24 12:49:31 BGP: sockopt_tcp_signature: setsockopt(13): Protocol not available
2021/09/24 12:49:31 BGP: can't set TCP_MD5SIG option on socket 13: Protocol not available

I hope someone might help in order to fix that, and enable the necessary kernel option.
Thanks in advance!