Here is initial firmware for upgrade from stock

OpenWRT for ASUS AC58U with LTE,ipv6, ipsec, zabbix agent support with 256 MB RAM (wifi firmware for big memory)
OpenWrt 23.05.3 for TP-Link c6u v1 , lte, wireguard, zabbix agent,ipv6
OpenWrt 23.05.3 for TP-Link c6u v1 , lte, wireguard, zabbix agent,modeminfo,ipv6

Here is OpenWrt 23.05.3 firmware versions Upgrade only from openwrt, not factory !

ASUS AC58U with LTE, ipsec, zabbix agent support with 256 MB RAM (wifi firmware for big memory)
tplink_archer-c6u-v1 c LTE,ipv6,ipsec,zabbix-agent
tplink_archer-c6u-v1,lte, wireguard, zabbix agent,ipv6
tplink_archer-c6u-v1,lte, wireguard, zabbix agent,modeminfo,ipv6 ASUS AC58U 256MB RAM,lte, wireguard, zabbix agent,modeminfo,ipv6