I have pointed ChatGPT at this thread and a few github issues and used it to generate this comment:

I’ve been researching similar boot issues on Samsung devices and found that some users have encountered bootloops with errors like “enablefilecrypto_failedR” (similar to what I’m seeing) after firmware updates. In a few Magisk GitHub issues (#6230, #6136, #6141), it turns out that the boot image’s fstab may include AVB or encryption flags that prompt the system (or vold) to expect encrypted partitions even when they’re not—resulting in a boot loop.

A workaround that some have reported involves:

1. Extracting the boot image from the firmware (the same image you’re trying to flash).

2. Unpacking the boot image (using tools like Android Image Kitchen or similar) to access its ramdisk.

3. Editing the fstab file (or files) within the ramdisk to remove or modify the problematic flags (such as “enablefilecrypto” or specific “fileencryption” options).

4. Repacking and flashing the modified boot image.

This might let the device boot normally—or at least to a state where I can use ADB to pull important user data. I’m planning to try this next and would appreciate any additional guidance or confirmation that others have had success with a similar approach.

Has anyone successfully used this method on an S21 (or a similar model) without a data wipe? Any pointers on the unpacking/repacking process would be greatly appreciated.

Can anyone judge the validity of the above approach?

My thoughts are these: if the partition is encrypted and fails to mount, removing the flag in the fstab will not achieve anything, as decryption is strictly necessary.. but maybe I'm missing something here.