I believe @Molski asked whether you simply replaced the content of mkinitcpio.conf with that of mkinitcpio.conf.pacnew, in an attempt to establish whether that might have been the cause of the subsequent boot failure.
Once the large update has been performed, use of the following ISO file might be prudent from that point on, or until the respective ISOs are made available from Manjaro Downloads.
Links to the Anh-Linh 25.1-pre1 (2025-12-08) ISO for your preferred Manjaro edition can be found in the Stable Update 2025-12-08 thread under the heading Additional Info.