alright, go through the ubuntu installer and pick the “install alongside” option when it comes up. it ought to be at the same time that it offers you the option to erase the disk altogether. the “installation type” menu. if you don’t get that option, stop and say so.
e: i just finished installing ubuntu desktop lts alongside windows 11 in a vm using the process you’re doing. its the disk selection menu, not the installation type.