If you have a disk image with multiple partitions, this type of image is used a lot for the raspberry pi, you can easily mount them using kpartx, you can install kpartx as follows

# arch linux / manjaro
sudo pacman -S multipath-tools

# ubuntu 20.04
sudo apt install kpartx

# centos 8
sudo yum install kpartx

Maybe you need to insert the loop module, if so you can do that like this

sudo modprobe loop

After that you can create the loop devices for all partitions in a image file with the following command

sudo kpartx -av image_file.img

You can now try to mount the different loop devices, see the output of kpartx

When you are ready and unmount all the loop devices, clean up the loop devices by running the following command

sudo kpartx -d image_file.img