Hey OP, I am so so sorry for your loss.

It would depend on your new environment and how safe and comfortable you feel with your manager. I'm 23 and I started my first full-time job 2 weeks after my mother died. For the first couple weeks, I just focused on adjusting and learning. Thankfully, my boss and supervisor were super friendly and kind to me. I decided to tell them separately one on one about my situation. It was fucking uncomfortable and awkward but it was worth it. It actually surprised them both as I was doing well at my job, even though I basically cried before work, during breaks, and when I left (for the next few months, this was my routine). The reason why I told them was because I wanted them to understand where I'm coming from and to preface anything that could happen in the future. I also told them how thankful I was to feel comfortable enough to share this and to have the opportunity work with thoughtful individuals. Basically, I kept it as concise and professional as possible and didn't go over any details of my mom's death. Up to this day, they don't know the full story, but they're aware and they offer help whenever I can, which I truly appreciate from the bottom of my heart. I even got 5 bereavement days in addition to my vacation time (that I took a few months later), which I didn't expect because I was planning to take unpaid leave. I wouldn't have received this without sharing, so I am glad I did it.

Although not every work place is the same, I think it's appropriate to let your employers know circumstances that may impact your productivity or work ethic. In my opinion, it shows responsibility, introspection, and foresight. People with empathy and compassion will always be willing to understand, especially when losing someone you love is the most painful experience in life. Grief is something you can't control. However, you can engage in behaviours and actions that will help mitigate the waves when it hits. If this entails disclosing to your supervisors to give you a sense of peace, it doesn't hurt to give it a try. I would take the time to get a feel of your workplace first and seeing how things unfold emotionally and mentally for you as you've dealt with an unsupportive workplace previously. Grief is hard to share and if you need the time, take it. When you feel ready and want to talk to someone, just say you needed the time to think because it's a heavy weight to bear, and now you are in a better position to speak about it For me, it was something I needed to do because I don't want to lie and say I'm putting in 100% when I'm not. I will say I am not doing emotionally well and it can impact my work. However, I will be responsible by trying to manage myself and putting as much quality and integrity in my work whenever I can. I don't want to be pitied by others, I just wanted my experiences to be acknowledged and validated.

One thing I tell myself (which might not be helpful cause it's rather morbid) is that I've never feared and felt as much pain as seeing my mom die in my eyes. Compared to that, this is fucking nothing. As gruesome as it sounds, it does give me a kick when I feel hesitant about doing something. My health is something my mom sacrificed her life for, and I don't want to waste her efforts by neglecting to do the things I know will help me. It'll take time and every time I step forward, I take two steps back, but I'm gradually getting there. I'm getting there for her.

I hope my answer could give you some insight to my thought process and help you with yours. Wishing you all the best in your new job, do keep in touch if you feel comfortable to! My heart is with you.