how to view newly processed help files

[Jack]

I think this might be a new twist on an old issue.  When editing  
docbooks, I set up a separate folder outside the source tree, and from  
there I run "meinproc5 path/to/index.docbook" and separately copy over  
the necessary png files.  I just did this, and typed "khelpcenter  
index.html" and was surprised that khelpcenter did open, but the manual  
opened not in khelpcenter, but in firefox.  I even tried "konqueror  
index.html" and the same thing happened.  I recall discussions that  
meinproc5, without using explicit stylesheets, produced html best  
viewed in a KDE browser, such as khelpcenter or konqueror, which is  
what I always recall doing.  It's been a while since I've tried this,  
so I have no idea how many different components have been upgraded in  
the meantime.  I can imagine file associations controlling what  
application is used if you click on a file in a file manager, but don't  
think I've ever seen it override an explicit invocation of an  
application and file.

I currently have khelpcenter-5.7.6.21043, meinproc5 5.0, frameworkd  
5.85.0, plasma 5.22.5, and kde applications 21.04.3 (generally Gentoo  
stable versions).

What am I missing or forgetting, or has something really changed here?

Thanks for any clues.

Jack