Hi Manuel,
Please share your infrastructure and configuration to help you access SMB from the Internet. However, I'd like to express my disappointment at accessing your LAN resources without a VPN... especially with a protocol like SMB. This is a real shame.
Also, if you want a firewall in AP mode, access from the WAN port, and the ability to use IP instead of KeenDNS, why did you choose Keenetic and not another brand? We focus on KeeneticOS, and, as you said, many people use our router, and we haven't received any such requests. There are many open-source alternatives that can achieve excellent results, such as PFsense, OPNsense, OpenWRT, etc.