AFAIK there isn’t any other Brave documentation to reference. I agree, there should be something somewhere, but I can’t find it. I could not find any documentation at Brave GitHub Wiki or the Chromium Project either. Doesn’t mean it isn’t there, just means I couldn’t find it!
I think this post below will probably help more but I do not know anything about macOS so can’t evaluate if this particular information is reliable. May not be since it shows 10.12.6 still supported. The post was “as of” February 2022, so the decision not to support may have been made after that date or it could just be wrong.
You may want to consider upgrading your macOS if you can especially since Sierra doesn’t seem to have had any security updates from Apple in quite a while. Posted two articles below that may be of help.