Re: file fmutil

Greg, I wonder if PATH that fmtutil is running with is somehow not the
same PATH as you are running from the command line.

Are you still trying to get this to work under TeXstudio (or another
frontend), or does the error happen on the command line? If it's only
TeXstudio, I would guess you need to configure the frontend, somehow.
(I've never used them, so don't know specifics.)

There's also a question of why mktexfmt is being run at all, since
installation normally creates all the .fmt files (unless you explicitly
disabled that). Which also, together with your question about
/usr/share, sounds like the frontend is not finding your TL25
installation, and is instead using what's on the system
(/usr/bin/... instead of /usr/local/texlive/2025/...).

Finally, can you try adding these two debugging lines to your fmtutil.pl
and show us what the output is? (I rather suspect a different fmtutil.pl
is being called and you won't see this output.)

--- fmtutil.pl	(revision 76944)
+++ fmtutil.pl	(working copy)
@@ -17,2 +17,4 @@ BEGIN {
   $TEXMFROOT = `kpsewhich -var-value=TEXMFROOT`;
+  warn "PATH=$ENV{PATH}\n";
+  warn "got: $TEXMFROOT\n";
   if ($?) {