I'd like to know what ～じゃてえ exactly means when located at the end of verbs and/or adjectives. Do young people use it rhetorically?
The whole sentence is:
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It's not a recent slang word but a dialectal form of だって or だな. It's probably still in use in some parts of western Japan*, but it may be best to consider it as a stereotyped role word of old people and people in rural areas.
* Both のう and じゃ are actively used in reality in Setouchi region. Some source say じゃて(え) is Okayama dialect.