ColinJK

Baby steps here. I gave HA a go a couple of years ago, and found it too cumbersome to configure. But I gave it a go 6 month's ago, and found it to be a lot more intuitive, as HA itself is now much more "easier" for noobs like me. Still have a lot to learn, but yesterday managed to use @Sc00bs's pool automation to switch on the pump only if there is a good solar forecast. 

I think one can understand that Solar Assistant can only perform as a one size fits all because it's a generic type of product. On the one hand if it was tailored for each case use just imagine the work required & how would you package such a product. I totally agree that HA is much more customized & one can concentrate the info of interest. However, I do agree it's not asking much to allow phase individual power charts to be exposed. That's not so far beyond the imagination of the humble user. Cell voltage delta on the other hand that may be a more advanced type of information package. 
I guess it's hard to strike a balance between an advance user & a new user. But I have to Vito HA it's on another level, however, you have to know what you up to to be able to extract what you want. 

The data is  available in the Sunsynk/DEYE Modbus queries so don't see any reason why they wouldn't be able to.
Otherwise I think that @slipx 's YAML code for ESPHome will probably query your inverter and pull that data as default:

Glad it helped @Sidewinder , BTW I have found ChatGPT to be of huge assistance with my automations. 
You just need to double check everything afterwards as it is quite often not 100%

@ColinJK,
After using SA for many years, I have moved away from it, but only because my enquiring nature is not satisfied with SA at this moment. Even though it provides good info, but if you are of an analytical nature,  then a HA system has given me endless more info, e.g. like the ability to graph cell differential voltages. 
So I would never picked up these huge deviations, unless I stare at the HA screen for many hours on end.
It is a mission and a half (for me) to get to this stage, most of which is discussed right here on PF!! The rest came from UOYT (University of YouTube)/Google😀

@Sidewinder That is very cool! Maybe one day, when I have a system of my own to tinker with 😅

@Steve87 I agree HA is not an alternative to SA in this instance, but grateful to Sidewinder for giving a glimpse of what could be possible!
SA is a cool product that does a nice job. But I'm irked that there is false advertisement. Sure, perhaps they didn't realise it at first, but after I wrote to them I would have hoped that they update their website at least with a note on the Deye etc guide that this particular feature, which I don't think is unreasonable to expect and is clearly shown on screenshots on their help page, is not yet implemented.

@Steve87 I agree HA is not an alternative to SA in this instance, but grateful to Sidewinder for giving a glimpse of what could be possible!
SA is a cool product that does a nice job. But I'm irked that there is false advertisement. Sure, perhaps they didn't realise it at first, but after I wrote to them I would have hoped that they update their website at least with a note on the Deye etc guide that this particular feature, which I don't think is unreasonable to expect and is clearly shown on screenshots on their help page, is not yet implemented.