yast2-iplb is not part of openSUSE Leap 15. It exists only in openSUSE Tumbleweed and enterprise products.
The translation of yast-iplb contains large help strings (2541 words; search for Source string location src/include/iplb/helps.rb). If you want to save your work, you can decide to skip all of them. The application will be still fully translated with exception of help texts.