any suggestions on how to have grantpt() be successful or not be attempted?

The issue arises because HAVE_GRANTPT is defined when building IO::Tty.
I don't know why that symbol is defined. It appears to NOT be defined by IO::Tty.
One possible solution (which should avoid the call to grantpt) is, in IO-Tty-1.20 source, to apply this simple patch to Tty.xs:

--- Tty.xs    2023-12-29 04:53:07.000000000 +1100
+++ Tty.xs_modified    2024-06-23 20:25:51.411610800 +1000
@@ -257,6 +257,7 @@
     {
     mysig_t old_signal;
     old_signal = mysignal(SIGCHLD, SIG_DFL);
+#undef HAVE_GRANTPT
 #if defined(HAVE_GRANTPT)
 #if PTY_DEBUG
     if (print_debug)
[download]

Then rebuild and reinstall IO-Tty-1.20.

Cheers,
Rob