There are probably too many networking tools which interfere with each other. Especially, I would either use systemd-networkd or connman, but not both (at least not on the same interface).
Try disabling connman using:
systemctl disable connman.service
Also you seem to have two DHCP server enabled, dnsmasq as well as systemd-networkd… I would recommend use systemd-networkd only to configure the IP address. Remove the DHCPServer=yes configuration.