oneplus 6 userdata not expanded during install

Describe your issue

After installing postmarketOS onto a Oneplus 6, the partition layout leaves close to no space for installing additional apps:

Filesystem                Size      Used Available Use% Mounted on
/dev/dm-1                 2.1G      2.0G     10.1M  99% /
/dev/dm-0               221.1M     56.4M    152.9M  27% /boot
tmpfs                     1.5G      2.1M      1.5G   0% /run
dev                      10.0M         0     10.0M   0% /dev
shm                       3.7G         0      3.7G   0% /dev/shm
tmpfs                     4.0M         0      4.0M   0% /sys/fs/cgroup
tmpfs                   756.0M     56.0K    755.9M   0% /run/user/10000

sda17 looks to be the main partition and lsblk shows the full size:

NAME    MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
sda       8:0    0 116.1G  0 disk 
├─sda1    8:1    0     8K  0 part 
├─sda2    8:2    0    32M  0 part 
├─sda3    8:3    0     1M  0 part 
├─sda4    8:4    0     1M  0 part 
├─sda5    8:5    0   512K  0 part 
├─sda6    8:6    0   512K  0 part 
├─sda7    8:7    0   256M  0 part 
├─sda8    8:8    0    10M  0 part 
├─sda9    8:9    0    10M  0 part 
├─sda10   8:10   0   7.9M  0 part 
├─sda11   8:11   0  15.8M  0 part 
├─sda12   8:12   0   512K  0 part 
├─sda13   8:13   0   2.8G  0 part 
├─sda14   8:14   0   2.8G  0 part 
├─sda15   8:15   0   100M  0 part 
├─sda16 259:0    0   100M  0 part 
└─sda17 259:1    0   110G  0 part

resize2fs does not seem to work:

oneplus:~$ sudo resize2fs /dev/dm-1
resize2fs 1.47.0 (5-Feb-2023)
The filesystem is already 571648 (4k) blocks long.  Nothing to do!

oneplus:~$ sudo resize2fs /dev/sda17
resize2fs 1.47.0 (5-Feb-2023)
resize2fs: Resource busy while trying to open /dev/sda17
Couldn't find valid filesystem superblock.

What's the expected behaviour?

The full 110Gb of data should be available to pmOS.

What's the current behaviour?

Only the operating system fits onto the disk, there is no room for new applications to be installed.

How to reproduce your issue?

I've installed manually using pmbootstrap and following the documented steps.

pmbootstrap init
pmbootstrap install 
fastboot erase dtbo
pmbootstrap flasher flash_rootfs --partition userdata
pmbootstrap flasher flash_kernel

What device are you using?

Oneplus 6

On what postmarketOS version did you encounter the issue?

• edge (master branch)

• v23.06

• v22.12 (Supported until 2023-07-06)

• I confirm that the issue still is present after running sudo apk upgrade -a

On what environment did you encounter the issue?

Environments

• GNOME Shell on Mobile
• Phosh
• Plasma Mobile
• Sxmo (Wayland/Sway) Please post the output of sxmo_version.sh
• Other: Please fill out

How did you get postmarketOS image?

• from https://images.postmarketos.org
• I built it using pmbootstrap
• It was preinstalled on my device

What's the build date of the image? (in yyyy-mm-dd format)

The images were built manually using pmbootstrap on 2023-07-25

Additional information