The typo3 library has served us pretty well over the years. Specially when we had to convert all the Moodle sites to unicode and later for core_text, as fallback whenever iconv (now required) and mbstring (still recommended) were not available.
This issue is about to:
1) Evaluate if, once we start requiring the mbstring extension for Moodle 3.9 and up (see
MDL-65809) we need the library (that is really huge and massive) anymore.
2) Change all current uses (core_text mainly) to work without it, ensuring that nothing is broken in the process.
3) Plan the standard deprecation and removal of the lib from core.