The changeset for 38 is typically extensive. Possibly the most controversial was the change to globally build with -fno-omit-frame-pointer to facilitate better profiling and debugging, particularly where debugging information is not available, but at a cost as this also takes a register out of circulation to hold the frame pointer. The performance impact seems to be limited on x86_64 but I doubt much testing was done on ppc64le, and it should be noted that PowerPC is one of the gcc targets where leaf functions wouldn't use a frame pointer anyway. Time will tell if this pays off. Builds are also now made with _FORTIFY_SOURCE=3 (up from 2) for better security, and another interesting though probably irrelevant change for most is reducing the shutdown timer in systemd to 45 seconds from 2 minutes.
On the back-end F38 ships with kernel 6.2.x and gcc 13, LLVM 16, gmake 4.4, binutils 2.39, glibc 2.37 and gdb 12.1. F38 also has a major upgrade to microdnf as dnf5, the "future of package management" that may ultimately replace dnf entirely. On the front-end F38 updates GNOME to version 44, finally with grid thumbnail view in the file picker, a big overhaul to the Settings app and many new applications, as well as more apps moving to the unthemable libadwaita (but I run KDE Plasma now, and haven't looked back). Xfce also updates to 4.18, there's a new spin for the Sway window manager, and the SDDM display manager now also defaults to Wayland (we use a text boot to log in and start X11 manually, avoiding any display manager completely).
This is the first release to include the change that blocks clients with different endianness from connecting to the X server, including XWayland, which means that the compositor has to support the configurable option too (GNOME 44 Mutter does, others may not). At least you still have the option!
We'll give the mirrors a week or two to catch up on builds and then start the transition on our own machines, with the usual mini-review to follow. Stay tuned.