Sorry but it still does not work.
root@GL-X750:~# uci export network
package network
config interface 'loopback'
option device 'lo'
option proto 'static'
option ipaddr '127.0.0.1'
option netmask '255.0.0.0'
config globals 'globals'
option ula_prefix 'fd52:4828:3011::/48'
config device
option name 'br-lan'
option type 'bridge'
list ports 'eth1'
config device
option name 'eth1'
option macaddr '94:83:c4:50:0a:c3'
config interface 'lan'
option device 'br-lan'
option proto 'static'
option netmask '255.255.255.0'
option ip6assign '60'
option isolate '0'
option ipaddr '192.168.10.1'
config device
option name 'eth0'
option macaddr '94:83:c4:50:0a:c2'
config interface 'wan'
option device 'eth0'
option proto 'dhcp'
option force_link '0'
option ipv6 '0'
option classlessroute '0'
config interface 'wan6'
option proto 'dhcpv6'
option disabled '1'
option device '@wan'
config interface 'tethering6'
option proto 'dhcpv6'
option disabled '1'
option device '@tethering'
config interface 'wwan6'
option proto 'dhcpv6'
option disabled '1'
option device '@wwan'
config interface 'guest'
option force_link '1'
option type 'bridge'
option proto 'static'
option ipaddr '192.168.9.1'
option netmask '255.255.255.0'
option ip6assign '60'
option multicast_querier '1'
option igmp_snooping '0'
option isolate '0'
option bridge_empty '1'
option disabled '1'
config interface 'wwan'
option proto 'dhcp'
option classlessroute '0'
config interface 'modem_1_1_2_6'
option proto 'dhcpv6'
option disabled '1'
option device '@modem_1_1_2'
config rule 'policy_direct_rt'
option lookup 'main'
option suppress_prefixlength '0'
option priority '1100'
config rule 'policy_default_rt_vpn'
option mark '0x8000/0xc000'
option lookup '8000'
option priority '1101'
option invert '1'
config rule6 'policy_direct_rt6'
option lookup 'main'
option suppress_prefixlength '0'
option priority '1100'
config rule6 'policy_default_rt_vpn6'
option mark '0x8000/0xc000'
option lookup '8000'
option priority '1101'
option invert '1'
config rule 'policy_default_rt_vpn_ts'
option lookup 'main'
option priority '1099'
option mark '0x80000/0xc0000'
option invert '0'
config interface 'modem_1_1_2'
option apn 'airtelwap.es'
option proto 'qmi'
option device '/dev/cdc-wdm0'
option node '1-1.2:1.4'
option username 'wap@wap'
option password 'wap125'
option metric '40'
option roaming '1'
option band_enable '0'
option disabled '0'
config interface 'wgclient'
option proto 'wgclient'
option config 'peer_2001'
option disabled '0'
root@GL-X750:~# wg show
interface: wgclient
public key: xxxxxawwm+KbjzExxxxxx9ArpBco8nRw=
private key: (hidden)
listening port: 51323
fwmark: 0x8000
peer: xxxxxxxM=
endpoint: xx.xx.216.231:51820
allowed ips: 0.0.0.0/0
latest handshake: 1 minute, 7 seconds ago
transfer: 352.23 KiB received, 450.72 KiB sent
persistent keepalive: every 25 seconds
root@GL-X750:~# cat /etc/config/firewall
config defaults
option input 'ACCEPT'
option output 'ACCEPT'
option forward 'REJECT'
option synflood_protect '1'
config zone
option name 'guest'
option network 'guest'
option output 'ACCEPT'
option input 'ACCEPT'
option forward 'ACCEPT'
config zone
option name 'lan'
list network 'lan'
option input 'ACCEPT'
option output 'ACCEPT'
option forward 'ACCEPT'
config zone
option name 'wan'
list network 'wan'
list network 'wan6'
list network 'wwan'
list network 'modem_1_1_2'
option output 'ACCEPT'
option forward 'REJECT'
option masq '1'
option mtu_fix '1'
option input 'DROP'
config zone 'wgclient'
option name 'wgclient'
option output 'ACCEPT'
option mtu_fix '1'
option network 'wgclient'
option input 'ACCEPT'
option masq6 '0'
option forward 'DROP'
option enabled '1'
option masq '0'
config forwarding
option src 'lan'
option dest 'wan'
option enabled '0'
config rule
option name 'Allow-DHCP-Renew'
option src 'wan'
option proto 'udp'
option dest_port '68'
option target 'ACCEPT'
option family 'ipv4'
config rule
option name 'Allow-IGMP'
option src 'wan'
option proto 'igmp'
option family 'ipv4'
option target 'ACCEPT'
config rule
option name 'Allow-DHCPv6'
option src 'wan'
option proto 'udp'
option dest_port '546'
option family 'ipv6'
option target 'ACCEPT'
config rule
option name 'Allow-MLD'
option src 'wan'
option proto 'icmp'
option src_ip 'fe80::/10'
list icmp_type '130/0'
list icmp_type '131/0'
list icmp_type '132/0'
list icmp_type '143/0'
option family 'ipv6'
option target 'ACCEPT'
config rule
option name 'Allow-ICMPv6-Input'
option src 'wan'
option proto 'icmp'
list icmp_type 'echo-request'
list icmp_type 'echo-reply'
list icmp_type 'destination-unreachable'
list icmp_type 'packet-too-big'
list icmp_type 'time-exceeded'
list icmp_type 'bad-header'
list icmp_type 'unknown-header-type'
list icmp_type 'router-solicitation'
list icmp_type 'neighbour-solicitation'
list icmp_type 'router-advertisement'
list icmp_type 'neighbour-advertisement'
option limit '1000/sec'
option family 'ipv6'
option target 'ACCEPT'
config rule
option name 'Allow-ICMPv6-Forward'
option src 'wan'
option dest '*'
option proto 'icmp'
list icmp_type 'echo-request'
list icmp_type 'echo-reply'
list icmp_type 'destination-unreachable'
list icmp_type 'packet-too-big'
list icmp_type 'time-exceeded'
list icmp_type 'bad-header'
list icmp_type 'unknown-header-type'
option limit '1000/sec'
option family 'ipv6'
option target 'ACCEPT'
config rule
option name 'Allow-IPSec-ESP'
option src 'wan'
option dest 'lan'
option proto 'esp'
option target 'ACCEPT'
config rule
option name 'Allow-ISAKMP'
option src 'wan'
option dest 'lan'
option dest_port '500'
option proto 'udp'
option target 'ACCEPT'
config include 'nat6'
option path '/etc/firewall.nat6'
option reload '1'
config rule 'block_dns'
option name 'block_dns'
option src '*'
option dest_port '53'
option target 'REJECT'
option device 'br-*'
option enabled '0'
config include 'gls2s'
option type 'script'
option path '/var/etc/gls2s.include'
option reload '1'
config include 'glblock'
option type 'script'
option path '/usr/bin/gl_block.sh'
option reload '1'
config forwarding
option src 'guest'
option dest 'wan'
option enabled '0'
config rule
option name 'Allow-DHCP'
option src 'guest'
option target 'ACCEPT'
option proto 'udp'
option dest_port '67-68'
config rule
option name 'Allow-DNS'
option src 'guest'
option target 'ACCEPT'
option proto 'tcp udp'
option dest_port '53'
config include 'vpn_server_policy'
option type 'script'
option path '/etc/firewall.vpn_server_policy.sh'
option reload '1'
option enabled '1'
config forwarding 'wgclient2wan'
option src 'wgclient'
option dest 'wan'
option enabled '1'
config forwarding 'lan2wgclient'
option src 'lan'
option dest 'wgclient'
option enabled '1'
config forwarding 'guest2wgclient'
option src 'guest'
option dest 'wgclient'
option enabled '1'
config forwarding 'wgclient2lan'
option src 'wgclient'
option dest 'lan'
option enabled '1'
config forwarding
option dest 'guest'
option src 'wgclient'
config rule 'glservice_https'
option name 'glservice_https'
option dest_port '443'
option proto 'tcp udp'
option src 'wan'
option target 'ACCEPT'
option enabled '1'
root@GL-X750:~#