This isn’t a phrase to describe them, but I heard this expression growing up: “mind your own beeswax!” I suspect it originated as a funny variant on “mind your own business,” meaning “don’t be so concerned with the business of others.”
More words for busybody, not used as often modernly but people will generally know what you mean:
“buttinsky” (they “butt in” to other’s business),
“nosy Parker” (not sure of the origin of this, though “nosy” by itself is also an adjective for a person who is curious and inquisitive into things others would prefer keep private),
“snoop” (this is a noun or a verb, a prying person and the action of prying into private things),
yenta (this is from Yiddish but is used in English sometimes; originally a yenta was a matchmaker, a marriage-arranger, but it came to mean someone who was always involved in the affairs of others);
All these courtesy of https://www.thesaurus.com/browse/busybody
“he has his nose in everyone’s business.”
“Kibitzer” - a person who doesn’t have a hand of cards to play themselves, but looks over the shoulders of players’s to see their hands and tells them how they ought to play (especially if they look at more than one hand and base their advice on that knowledge). This is sometimes used out of the playing card context for someone who always tells other people how they should do a task or live their life. Kibitz can also be a verb, and the participle kibitzing.
Here is an idiomatic phrase: “back-seat driver.” Similar to kibitzer, it came from literally someone sitting in the back seat of a car who constantly second-guesses the driver’s decisions, tells them they should be doing something else, etc, but quickly became a metaphor for telling others how to run their life.