Gapps: Could not mount /mnt/system!

[BIG1]

• [ X] I am running an official build of TWRP, downloaded from https://dl.twrp.me/chagalllte/
• [X ] I am running the latest version of TWRP
• [X ] I have read the FAQ (https://twrp.me/FAQ/)
• [ X] I have searched for my issue and it does not already exist

Device codename: Samsung SM-T805 chagalllte using Lineageos 20 with android 13.
https://xdaforums.com/t/rom-unofficial-13-lineageos-20-for-samsung-galaxy-tab-s-10-5-sm-t805-sm-t800-chagalllte-chagallwifi-alpha.4577223/
TWRP version: twrp-3.7.0_9-0-chagalllte.img.tar

WHAT STEPS WILL REPRODUCE THE PROBLEM?

Have tried to install mindthegapps and nikgapps without success in twrp.

WHAT IS THE EXPECTED RESULT?

Successfully install.

WHAT HAPPENS INSTEAD?

Could not mount /mnt/system!
Here is the screenshot:
https://xdaforums.com/attachments/20240130_220243-jpg.6061984/

ADDITIONAL INFORMATION

After googling the issue it seems like I have to use Lineageos recovery. But I want to use twrp.

[Igorpetinik]

use recovery from custom firmware, for example: flash LineageOS via lineageOS recovery, and after flashing LineageOS flash GApps via LineageOS Recovery.

[Igorpetinik]

TWRP can't flash GApps, you can flash lineageos recovery, flash GApps, and after installation GApps - install TWRP