Gut Shabbos / Gut Yom Tov.
“Shabbat” is a Sefardic pronunciation. The Ashkenazic pronunciation is “Shabbos”. Traditionally Ashkenazim say “Gut Shabbos”. Someone pronouncing it as Shabbat who isn’t Sefardic is doing so for zionistic reasons and is changing their traditional minhag, something they should not do.,