Clean LineageOS 17.1 install and empty device - can't work out how to mount data partition in TWRP? I'm installing LineageOS 17.1 on my new phone. It works fine, but I can't get to data in TWRP.
As usual, to install, I wipe everything, drop into TWRP, format (not just wipe) data, wipe cache/davlik/system, and flash the LineageOS installer file. When the system starts first time, it gives a message &quot;encrypting data&quot;, which doesn't have a &quot;skip&quot; option.
When I drop back into TWRP it asks for a decryption password to access data, but I don't have one because I haven't entered one in the first place.
How do I get LOS to not encrypt data, or alternatively, what decryption password should I use in TWRP?
Note: this isn't a duplicate question. Other questions about decrypting data involve corrupt data or system issues that prevent data being accessed because of encryption, or trying to recover files from data. In my case, it's a clean install with no prior data content, but I can't figure how to access data in TWRP because it seem to encrypt it automatically but there's no hint what key to enter in TWRP.
First let's have a look why it is not (yet) possible to mount encrypted userdata partition from TWRP especially on Samung devices.
Encryption is hardware-backed in TEE and therefore vendor specific. Furthermore ...

... some vendors such as Samsung use their own encryption techniques. Without heavy deconstruction/decompiling of custom library blobs, and successful ports by an active maintainer, this may never be done.


TWRP FAQ
sandy framework DerbyCon 3.0

Decryption involves the underlaying firmware. It requires to mount various partitions and running libraries for communication with (TEE) Trusted Execution Environment.

Azeria TrustZone Research

For Qualcomm devices it is necessary to run qseecomd (for Exynos devices the Trustonic Kinibi daemon). In this example the modem partition is mounted with mounttodecrypt flag (qualcomm)
/firmware   vfat   /dev/block/bootdevice/by-name/modem   flags=slotselect;display=&quot;Firmware&quot;;mounttodecrypt;fsflags=ro

As we can see on this list of libraries also the vendor partition is mounted. This is also OEM specific content used by LineageOS and not included in TWRP by default
/firmware/image/cmnlib.b00
/firmware/image/cmnlib.b01
/firmware/image/cmnlib.b02
/firmware/image/cmnlib.b03
/firmware/image/cmnlib.mdt
/firmware/image/keymaste.b00
/firmware/image/keymaste.b01
/firmware/image/keymaste.b02
/firmware/image/keymaste.b03
/firmware/image/keymaste.mdt
/system/bin/linker64
/system/bin/qseecomd
/system/lib64/hw/keystore.qcom.so
/system/lib64/libbacktrace.so
/system/lib64/libbinder.so
/system/lib64/libcnefeatureconfig.so
/system/lib64/libc.so
/system/lib64/libcutils.so
/system/lib64/libEGL.so
/system/lib64/libgccdemangle.so
/system/lib64/libGLES_trace.so
/system/lib64/libGLESv2.so
/system/lib64/libgui.so
/system/lib64/libhardware.so
/system/lib64/liblog.so
/system/lib64/libm.so
/system/lib64/libnetd_client.so
/system/lib64/libsigchain.so
/system/lib64/libstdc++.so
/system/lib64/libstlport.so
/system/lib64/libsync.so
/system/lib64/libui.so
/system/lib64/libunwind-ptrace.so
/system/lib64/libunwind.so
/system/lib64/libutils.so
/system/vendor/lib64/libdiag.so
/system/vendor/lib64/libdrmfs.so
/system/vendor/lib64/libdrmtime.so
/system/vendor/lib64/libNimsWrap.so
/system/vendor/lib64/libQSEEComAPI.so
/system/vendor/lib64/librpmb.so
/system/vendor/lib64/lib-sec-disp.so
/system/vendor/lib64/libsecureui.so
/system/vendor/lib64/libsecureui_svcsock.so
/system/vendor/lib64/libssd.so
/system/vendor/lib64/libStDrvInt.so
/system/vendor/lib64/libtime_genoff.so
/system/vendor/lib64/libvendorconn.so


TeamWin github oneplus2


Now, as we know there is a lot of research to make decryption working, it's obviously TWRP maintainers are desperate overhelmed with providing encryption support for all devices. Therefore decryption is always only a goody, heavily depending on maintainers knowledge and engagement.
That might one reason why android modding scene prefer to run custom ROMs unencrypted

Encryption is forced since Android 5.0 with forceencrypt= flag in fstab (FDE) or fileencryption= (FBE)

source.android.com Full-Disk Encryption

The flags encryptable= forceencrypt= and forcefdeorfbe= are always pointing to crypto footer. Therefore they are interchangeable.

android.googlesource.com fs_mgr_fstab.cpp

To disable force encryption (FDE) use the first flag. Edit your fstab entry for userdata partition and replace forceencrypt= with encryptable=
/dev/block/platform/11120000.ufs/by-name/USERDATA   /data   ext4   noatime,nosuid,nodev,discard,errors=panic   wait,check,encryptable=footer,length=-20480,reservedsize=128M

This can be done from TWRP by installing no-verity-opt-encrypt-6.1.zip

no-verity-opt-encrypt-6.1.zip (FDE)

The benefit of having force encryption disabled while keeping the availability for encryption is in the nature of Direct Boot vs Secure Start. Upon first boot, the device creates a randomly generated 128-bit master key and then hashes it with a password and stored salt. The resultant hash is also signed through TEE (such as TrustZone), which uses hash of the signature to encrypt the master key. There are four kinds of encryption states:

default
PIN
password
pattern

On Direct Boot the former one is forced with 'default_password', indeed that's how most android devices still encrypted. (TWRP always probes against 'default_password' and only asking for password if decryption failes.)
If you choose Secure Start from security menu the keystore password is re-created using your current lock screen credentials. downside of this encryption state android won't boot until correct passphrase is entered.

To overcome this the benefits of Secure Start with Direct Boot was merged in (FBE) File-Based Encryption, which was introduced with Android 7.0 and enforced for devices shipped with Android 10+
Be aware there is no way to disable enforcement of (FBE) File-Based Encryption. Therefore the only method left is to disable encryption completely by deleting the fileencryption= flag from fstab (with no proper replacement). Indeed that is how Magisk does currently when flashed from TWRP.
Universal DM-Verity ForceEncrypt Disk Quota Disabler will disable encryption completely

Universal DM-Verity ForceEncrypt Disk Quota Disabler (FBE)