Install Rocky Linux 9.3 in multi boot installation with Ubuntu and Mageia Linux

My system is a 16 GB memory, SSD disk 512 GB with Ubuntu and Mageia. N100 processor from Intel. Only for Linux distro’s. I use a try/install usb stick.
I try to install Rocky beside Ubuntu(sda2) en Mageia(sda8). My swap = sda4. (only one swap partition is enough) SDA 1 is fat32 /boot/efi .I use Standard Partition and wil make that sda7 will be used by Rocky. All partition for Linux distro’s are ext4. How do I make a good / root mounted partition. I used the guide for install 9.1.

So how did the install fail? Since you are not doing the default install you have to use the Custom installation selection. Once you select that and say done it should open a screen where you select the partition for install, sda7 in your case. You then have to click the box “Format to” and select ext4. You have to reformat even if it is already and ext4 partition. You also have to select the esp partition but do not reformat this or you will loose the other OS’s.
Without any more specific information it is just a bunch of guessing on our part.