When I generate to Microsoft HTML the CHM file does not show me the names of the topics because they are in cycillic, I only see those signs -, _, /.I have already set the language to Bulgarian in the Output Presets.
It's been a long time since I've generated chm and never in RH2019 New UI (I assume that's what you're using). In the past I think both Windows and the project needed to be set to the same language. Unfortunately that's my only suggestion.
We have made some fixes around this in update 11. Please try out after the update is available today.