Hi Tara,
There have been some good insights in this thread, but I just wanted to add my own perspective. I too have struggled with depression and a long-held existential/spiritual preoccupation.
First of all, I think there are a variety of different kinds of depression, stemming from a variety of things. These can range from issues with self-appearance, loneliness (or lack of community engagement), problems with brain chemistry, trauma, having a neurotic/melancholic personality, not taking care of the body, etc. To me, it seems like your primary concern is that you can't find a reason to exist in this world. You can find no meaning, an existential problem. That said, you should reflect if there are any other catalysts, because addressing some will often sooth the others. As others have said, make sure you're looking after your body and diet. Those two aspects are the easiest to remedy, and they have a huge influence on mood. Make sure you exercise and eat good food.
No one can give you a reason to live, a way to find meaning and fulfillment, but you can evaluate what is lacking. You mention you struggle enjoy work and community. But have you asked yourself if they are the best fit of work and community for you? Most people find work bearable for one or more of three reasons: Their work engages them with their community, their work allows them the funds to pursue their real passion, or their work is their real passion. Can you find work which will fulfil one of the criteria? Many people work solely to provide for their children/family, the ultimate form of community. Do you want to have a family one day? Many people find having children as the ultimate source of meaning. Is there a community with which you identify or would like to, or is there a group of people you would enjoy helping? If so, you might benefit from making engagement with this type of employment your primary goal.
If you can't now think of a community, then ask yourself what type of thing do you most enjoy doing? You should attempt to match your favourite types of actions to your employment. Do you most enjoy working with your hands? Then do something with your hands for work. Are you most happy when helping people with problems? Then maybe social work would fulfill you. Are you highly intellectually obsessed? Perhaps academia. Creative? Then find a creative job, or bear a job solely so you can fund your creative endeavour. What types of problems do you most like to solve? Are they spatial problems, organizational, creative, logical, personal, emotional, or something else? Your job and your community should be tied to one another, but also, ideally, to the types of activities you find enjoyable. People generally feel best about their work when they feel they are helping a community they are a part of and value. For some people, that community is simply comprised of the people in their workplace. For others, it will be much harder. You might have to seek an employment lifestyle which will make you feel communally involved. For me, I know I would like to have a family and I would like to fund my creative pursuits which probably won't be profitible financially, so that is enough reason to work. However, I've spent enough time working jobs I felt were meaningless and dull to know I need to do something which engages my interests. I'm only really satisfied when reading and writing and engaging intellectually, so I decided to go back to university in order to pursue a career in academic research. That's my goal.
Goals are important. If you can think of anything which might solve these issues, you should make that your primary goal, and this goal will give some sort of structure and meaning to your life in itself. If you can't for the life of you think of any worthwhile job or community, then you should make the search for them your primary goal. The search for meaning is what Albert Camus viewed asbeing at the heart of meaning itself, the fight against nihilism. To get a little bit spiritual, if you investigate the world, take in everything it has to offer, explore it to find yourself, you'll see the universe constantly unravelling the grandiosity of its sheer existence before you. Experience of existence is a gift we might only possess for a lifetime. Take the time to do many different things, talk to many different people, travel, in order to find your own personal meaning. Just don't be stagnant. If you need to get away from people to find a new community, do it. Be open. If you find your job completely unengaging and numbing, either find a way to make it better or leave it. Find a more fulfilling job/community ASAP, before it becomes more difficult (although its never too late). You don't have to fit in to mainstream society, but you can if you want.
On the matter of psychedelics for treating depression/existential crisis, it can be hit or miss. Some people report having all their problems being fixed by psychedelics, for others, it seems to have the opposite effect, opening their worldview up to negative aspects of existence which they previously hadn't perceived. Most people are somewhere in the middle. In my experience, I don't feel like psychedelics have ever had a lasting effect on treating my depression and existential dread. My first DMT experience did, however, seem to cure me of my lifelong preoccupation and fear of death. You might consider microdosing psilocybin mushrooms. Many people seem to report positive results with doing so.
If you do try a larger dose of a psychedelic, you might want to try meditating on some of these issues before you go into the experience (in a safe place, with set and setting in mind, of course). But psychedelics tend to take you in places you weren't anticipating anyway. I tend to find that most hallucinogens open me up to far more questions, without providing me the answers. The answers are for me to work towards myself. But sometimes those questions are exactly what is needed. You can't find the right answer without the right question. On the other hand, freebase DMT seems to provide me with answers to questions which I couldn't have even fathomed, but in a way that doesn't necessarily translate into everyday life and the search for meaning.
My only other advice is to read widely: fiction, philosophy, non-fiction, whatever, on many different topics and from many different perspectives. But that might just be the biased opinion of a book-worm.
I wish you all the best.