The word "plainne" is quite uncommon and difficult to find synonyms for. However, one possible synonym could be "blandness," which refers to the lack of flavor or interest in something. Other synonyms might include "simplicity," "unsophistication," or "minimalism," which all reference a lack of complexity or decoration. In some contexts, "plainne" might also be interchangeable with "dryness," "dullness," or "tediousness," indicating a lack of excitement or engagement. Ultimately, the choice of synonym will depend on the specific meaning and context of the word "plainne" in question.