Hello JIm
You wrote :
" Are LTspice XVII schematics still *.asc? If so, which program
version do you assign as "Open with"? "
I am surprised that YOU, a long user of LTspice ,? ask for such a question.
Why don't you try ?
1/ For sure schematics are still .asc
2/ There is a problem with windows to assign multiple versions od LTspice? (IV or XVII) with the fonction "Open with" of Windows. Perhaps ask to M. Enguelhart
Maybe I have not well understood ypur question.
Best Regards
PhB