On the connman and netfilter issue, below is the part of the README that deals with what needs to be enabled in the kernel config, and all exists in the current kernel build as either builtin or modules:
Kernel configuration
====================
In order to support tethering, the following kernel configuration options
need to be enabled either as modules (m) or builtin (y):
CONFIG_BRIDGE
CONFIG_IP_NF_TARGET_MASQUERADE
In order to enable CONFIG_IP_NF_TARGET_MASQUERADE, the following options need
to be enabled also as modules (m) or builtin (y):
CONFIG_NETFILTER
CONFIG_NF_CONNTRACK_IPV4
CONFIG_NF_NAT_IPV4