question

Simple answer is yes, this is not uncommon.

But, care needs to be taken around any common mode voltages that differ between your VE.Direct device and the RPi.

What you should do, is to place an isolator in between the two, so that there can not be any voltage differences, say between the zero volt lines.

As I understand it, most if not all VE.Direct ports do not have any or very much in the way of protection before the CPU.

So, now it depends if you are thinking of using serial over USB or plain async TTL between the two ?

There can be issues with USB, in that if at any time a serial connection becomes broken, say some data corruption, then generally, a serial over USB connection will remain disconnected. You don't get this with async TTL.

With USB, make sure you have the correct USB interface voltage on the TTL side. Often they provide a jumper for selecting 3.3V or 5.0V.

I have on a plane somewhere from Italy a nice little board that has 4 isolated TTL ports into a single USB port on its way. It even can come with the same JST connectors used for VE.Direct.

This allows you to then use a single USB port to then communicate with up to 4 async TTL devices, and in my case these will be SmartShunt, MPPT controller and RS 48| 6000 inverter. The 4th port will go to my own design BMS.

Like you, I do not use VenusOS and also do use RPi, but use Python to create a full SCADA application which does the lot. It's a lot of fun, so go for it :)