I've got the same issue. seems to be an issue due the new grub / systemd or calmares update.
Also got the same issue installing endavouros with the online installer.
Tried several usb sticks and different isos.
Used the dr4gonized iso and all times a encrypted install with luks.
Im not new to arch or to linux. Maybe considering to research the problem on the calmares installer or something with KDE/NVIDIA.
So that there is a issue in the endavouros iso and also your iso it really seems like a problem on calmares installer and not on user site. before I also runned arch and garudaos. both encrypted.
Take a watch