FWIW, I have two separate requirements, first of which is a remote computer behind a firewall and used by an individual with a communications issue. Once a week or so I need to assist this user by logging in to the computer and doing tasks when it is impossible to communicate what I need to get the user to do. Note particularly that I have a totally legitimate EPOA to manage the user's affairs.

Second situation involves management of two unattended remote computers monitoring an off-grid power system and a grid-connected PV system. Most of the time its simply a matter of checking battery voltage, load and PV output.

I have administrator access to all remote computers.

Before TeamViewer, I was running a fixed public IP on the latter computers and using RDP to connect, however that proved to be a red rag to the official scum. If all else fails, I may need to return to RDP but implementing a number of hardening measures. TeamViewer does what I need, but presently the company is attempting to harass 'free' users onto an extortionate subscription arrangement.

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