I just googled the Mikrotik Knot modbus device and I don’t see how it will work directly with Blynk.
Presumably you don’t have any WiFi coverage in the area where your solar charge controller lives?
I’ve done quite a bit of work on interfacing with my EPEVER solar controller and initially I used a an RS248 to serial converter and a Wemos D1 Mini.
It would be a fairly simple task to replace the Wemos with a cellular enabled board such as the TTGO T-Call ESP32 board.
Presumably you’d need to limit your cellular usage by either disconnecting and reconnecting from Blynk or using deepsleep, but that’s all doable.
I’ve now shifted away from the Wemos approach and use an Elfin EW-11 and query it from Node-Red then send the data to Blynk, but that is a WiFi only solution and you probably don’t want to go down the Node-Red route just for that anyway.
This topic contains a description of the Wemos hardware I was using…
More info, and a variation on the circuit board I used here…
A bit of info on how I use the data once it’s in Blynk…