Yes, but this is not possible via DynDNS, as you are most likely operating the device with a SIM card and the IP address is part of the internal address range of the mobile operator. However, since the RUT950 also has an integrated VPN client, this is possible. However, I access my OpenVPN server of my Synology NAS at my residence via the OpenVPN client of the Synology NAS (on the RUT950) of my second location. The second-location NAS is on an internet-controlled outlet and automatically starts the VPN connection when it boots up.

The socket solutions are all based on standard LAN (MaxSmart Power Station) or WLAN (myStrom and smart-me). All of the IP socket outlets mentioned connect as clients via the LTE router to their own external administration servers. The actual control is then carried out by smartphone apps via a connection from the user's own phone to the respective administration servers.
For the radiator valves in the holiday flat, I use TeleButler (which controls the temperature via SMS commands). This works absolutely without any problems. There are corresponding products for Wifi valves (e.g. Netatmo Vaves). Personally, I have no experience with these valves, as I use the TeleButler. However, I have a Netatmo weather station that works very well and, like the IP sockets described above, accesses the administration server as a client via the local Wifi signal and is read out by me via smartphone app, not directly in my second location LAN, but via the administration server. This means that there is no problem getting directly into the remote LAN via DynDNS and port forward (which fails with LTE internet connections due to the lack of a public IP address, unless you use a VPN client from the remote LAN as described above), as you only need to dial into the accessible external administration servers and the respective providers regulate the communication paths to their clients themselves.