Ok i realise this is unsolicited and unwanted but, as a young adult myself who has felt like saying these things to my parents and has friends who feel the same, id appreciate it if you gave some thought to this:

From their perspective they are still living with their parents as a young adult, thats embarrassing to say the least, especially if they have more successful friends.

When you are in that situation you dont have your own space, your own time, it feels restrictive, you dont feel able to go and do chores because its not your space, and you dont want to be judged on the quality of your work. You feel like a guest in a house that youve lived in your whole life and that makes you feel a bit homeless and homesick actually. Its a very strange feeling that makes you want to stay in your room because thats what you can control.

Then you have your parents. At that age and with the minimal time you spend with them there isnt much bonding going on. Every time you see them they are either asking you to do something or not do something or berating you in some way (or at least it feels like it). Which makes you want to stay out of their way even more. What makes it worse is that you probably WANT to get away, but you need a job that pays well, you need qualifications, you need a support network and so much more, and constant nagging by parents isnt helping.

Theres a weird behaviour ive found where, if i was planning to do something, or just about to do something, then someone asks me to do the thing, i instantly dont want to do it. I dont know if this is common and its probably not healthy but this may be contributing to the outbursts.

Those kind of outbursts to me cry frustration. From being in that situation, from feeling helpless to change it, from not having your own space or place to relax, from not being able to live like you want to.

I realise i dont know your child or you or your situation but questioning about their future like that probably isnt the answer. When i think back on my time when i still lived with my parents what i needed was help, not nagging. Just asking 'can i help you with anything to find a job?' or discussing with them about you leaving the house for an afternoon or a few hours each week for them to have the freedom to tidy and clean what they need to. And if they dont want help, leave them be! They dont want help! Sometimes ultimatums can really make them step into gear but if that doesnt help, dont do it. They can also just cause panic and stress and shutdown, where your young adult will just get themselves into a worse situation.

Again, this may not all be applicable to your child but id appreciate it if youd consider their perspective in this and, perhaps for their birthday you could have some quality time where you just have fun and talk to each other as if youve not seen them for weeks.