The included filters are here: Docs - Filter Reference
They are available in the backtrader.filters module
If you want the one from the blog post, you can simply copy the code and use in your own development.
The RSI in the def __init__(self): just does that. I wrongly assumed the indicator was doing its math on the csv data source. I did the math ant it computes on the Renko output data. Basically, this question was on a wrong assumption.
That was a regression bug introduced which affect the live brokers in version 1.9.57.122 (and probably 1.9.56.122)
See this Community - Broker and fundmode for a solution with stdstats=False for cerebro
Or update to the 1.9.58.122 (released today) which addresses the problem.
You probably want to elaborate with some code and data. As posted the error speaks for itself: python cannot convert the character " to a float, which is indeed something to be expected.
In this blog post, the described data feed is for the exported CSV data files or for direct usage of the binary (.fd or .min) which are of course static
For a real-time feed and trading broker for VisualChart you may want to look into:
Docs - Live Data Feeds and Live Trading / VisualChart
Blog - VisualChart Live Data/Trading
In the blog post introducing the feature you can see orders that were sent to VisualChart over the COM interface.
To take into account:
Test a lot. The code may contain bugs, your code may contain bugs and even VisualChart may contain bugs.
You need the python comtypes packaged detailed in the documentation. The Pull-Request hasn't yet been integrated into the main development tree (which seems more or less stopped from a development point of view)