diff -up asymptote-2.55/settings.cc.settings asymptote-2.55/settings.cc
--- asymptote-2.55/settings.cc.settings	2019-09-30 06:47:32.464160386 -0400
+++ asymptote-2.55/settings.cc	2019-09-30 06:48:48.419518013 -0400
@@ -98,9 +98,9 @@ string defaultPSViewer="open";
 string defaultPDFViewer="open";
 string defaultHTMLViewer="open";
 #else  
-string defaultPSViewer="gv";
-string defaultPDFViewer="acroread";
-string defaultHTMLViewer="google-chrome";
+string defaultPSViewer="evince";
+string defaultPDFViewer="evince";
+string defaultHTMLViewer="xdg-open";
 #endif  
 string defaultGhostscript="gs";
 string defaultGhostscriptLibrary="";