finalmente ci sono riuscito...
Franco sono riuscito a flashare con il TWRP 3.3.1.7, lo script va modificato in questo modo, al posto di inserire @android_root è sufficiente inserire /system_root, che stupidamente, usando il file manager del TWRP questo direttorio era ben visibile...
codice:
set_progress(0.01);
ui_print(" ");
ui_print("@G97X MODS by Carotix");
ui_print(" ");
set_progress(0.02);
############ Preparing Partitions ############
ui_print(" ");
ui_print("@Preparing Partitions");
ui_print(" ");
ui_print("Unmount partitions if mounted");
ifelse(is_mounted("/system_root/system"), unmount("/system_root/system"));
ifelse(is_mounted("/system_root/product"), unmount("/system_root/product"));
ifelse(is_mounted("/system_root/vendor"), unmount("/system_root/vendor"));
mount("ext4", "EMMC", "/dev/block/platform/13d60000.ufs/by-name/system", "/system_root/system");
mount("ext4", "EMMC", "/dev/block/platform/13d60000.ufs/by-name/vendor", "/system_root/vendor");
mount("ext4", "EMMC", "/dev/block/platform/13d60000.ufs/by-name/product", "/system_root/product");
set_progress(0.50);
delete_recursive("/system_root/system/app/XXXXX");
delete_recursive("/system_root/system/priv-app/1prova");
delete_recursive("/system_root/system/priv-app/xxxxx");
assert(package_extract_dir("system", "/system_root/system"));
assert(package_extract_dir("vendor", "/system_root/vendor"));
assert(package_extract_dir("product", "/system_root/product"));
ui_print("@Done");
questo il file di prova usato : https://www.mediafire.com/file/ynwk4..._ASG8.zip/file