I think you are likely to have to modify your installation. Things have moved on in 10 years.
Re the emonPi V1, there is a note on the downloads page and I think therefore you should be able to get the emoncms part working again. However, as you say, the minimum feed time is not as short as you would like (I think it is now 10s).
Do you still have access to the NodeRED flow? IME migrating NodeRED flows is a nightmare!
For directly matching your charging to excess solar, these devices are not really the best option. I think there are a number of dedicated solar diverters now available which may meet your need.