Add the --all-fields flag to the list subcommand to also see the SDK Directory column, which shows the directory name where the SDK files for the given version entry are located.
For example:
> nrfutil sdk-manager list --all-fields
Version SDK SDK Directory Toolchain
v2.9.0 Not installed Installed
v2.8.0 Installed v2.8.0 Installed
v2.7.0 Not installed Installed
v2.6.2 Not installed Installed
v2.6.0 Not installed Installed
v2.5.0 Installed v2.5.0 Installed