Asklemmy

You're asking about a collective and also a singular...

Just in general I'd say that if you're trying to quit a habit around trans women, go the extra mile and quit it around cis ones too. For the collective "hey guys" I have no one-word replacement ("folks/folx" sounds equally southern and somehow more cringe), but you could replace the whole phrase with "hey everybody", "hi gang", "how are you all", or just "hey".

When speaking to any woman, I would advise against calling them "dude" or "man." Full stop. No further thoughts necessary on that one.

I bit the bullet and was the cringy person at work who said "peeps". After a few months of do this, it was amusing to see the word spread until my boss's boss started saying peeps in meetings.

Fellow humans

Fellow Earthlings

for singular use boo works, and plural you can say "hey, fuckos"

"What is up, my mammals?"

"Mate" is always a good option, I wish it's used more universally in the States, too.

Peeps

Note: You will sound like a tool if you say this.

Fellow bipedal meat-things.

Dipshits

"What's up everypony?"

My go-to is folks, but 1000 others have mentioned that already. So I will throw in "people".

"Hey people, how's it going?"

That works for me

I just omit the unnecessary words or use their name. That works OK, although I'm awful with names so usually it just becomes "Good job!" or "What's up?".

Funny story time: in English I find this is not so bad. In French it's worse. In Vietnamese it's awful. We have dozens of pronouns. They're not only mostly gendered, but contain information about their age and perceived status relative to you. It's a 3-dimensional matrix where the axes are approximately gender, age/hierarchy, and degree of relation (inlaws/blood relations/strangers). You even get a different word for yourself in some of these situations. Then sometimes there's a numerical rank inside each pronoun e.g. male uncle, my spouse's family, 3rd oldest.

The language is already at maximum pronoun burden. Honestly it would just be easier if we called each other 'human' or 'comrade' or 'citizen' or something equally encompassing. It's exhausting as a non-native speaker (and you are not ever allowed to use their names, that's considered super rude).

You could copy Scooby do and refer to the group of people as 'gang', 'team' works too

Comrade

Greetings, Programs!

Gang

Peeps

Guy:innen

Folks for groups and friend for individuals is my go to. Comrade if you want to be spicy

all friends everyone folks peeps team

If you're only addressing one person then it can be left off entirely.

Buddy is masculine?

Friend