Does LUKS affect the upgrade in offline mode?
I had all packages installed and prepared for F42 upgrade. I have NVMe drive and I really don’t know why the upgrade was slow. Multiple times it got stuck for an hour on systemd/some-kernel/akmods/dns.
My upgrade was taking 5+ hours and I just turned the PC off. I have finished upgrading the packages from partially functional F42.
What do you do differently?
Instructions used:
Upgrading Fedora Linux Using DNF System Plugin :: Fedora Docs
This is a supported way of doing upgrades, and it shouldn’t have gotten stuck during the process. Though if you have akmods, I assume you have third-party kernel modules installed? That should work too, but installing non-Fedora packages can always cause surprises 
Nvidia only.
Does it makes sense to remove nvidia → make an upgrade → akmod on?
All that time I had been thinking LUKS was degrading the performance.
There are reports that akmods does not work well with off line updating.
Uninstall akmods then upgrade is a solution.
I have both VirtualBox and Nvidia drivers installed from rpmfusion.
I have never used offline upgrades but have instead always used the dnf system-upgrade download followed by the dnf system-upgrade reboot process from that Doc and have never had an issue with akmods or anything else during the upgrade.
Note that I do not use luks so cannot say what impact that may have on the process.
LUKS, nvidia drivers, and VirtualBox are all present on my system, and those instructions have worked without issues for Fedora upgrades over many years.