I've struggled with depression since my mid-20s. I've tried a lot of things to alleviate the symptoms, and some of them have worked. At various points I have taken medication for depression, which I strongly recommend in the short to medium term. Beyond that, there are small, practical things that seem to have helped me.
The Scrubby Brush
Get a stiff brush for the shower. This is the one I have. When you're in the shower, scrub your skin with the stiff side of the brush. I don't really know why this works, but it generates a similar sensation to cold plunging (the stinging sensation of cold water on your skin). If you search for this, you will find a lot of crazy claims (lymph node drainage! detoxification! etc). I don't think any of these are true, but the sensation is quite invigorating, and I find the improvement in mood lasts for a good few hours.
Playing with temperature ...
Saunas, steam-rooms, hot and cold showers = good. Often a 3+ day bump in my mood if I sit in a sauna for 30-40min. You also feel like you've exercised, but all you have to do is sit down in a hot room.
... and particularly cold water immersion
This is one of the most hyped "internet" treatments for depression, but I find that it works quite effectively. I go through periods where I do this regularly in the lake near my house, normally starting in the summer and tailing off toward the beginning of December. It's also possible to do in the shower. A key part of replicating it in the shower is to not do it gradually - you need to turn the temp fully from your normal shower temp to as cold as posssible, to get the "shock" effect. The objective is to get to the stage where you feel forced to take giant gasps of air, and then stay there for at least 30 seconds to a minute.
Delete Instagram/Twitter/Facebook/TikTok from your phone
Social media has extremely high positive utility - a lot of my professional network is on Twitter for example, and I get a lot of enjoyment out of watching food based content on Instagram. The main insight here is that you can still get these upsides without having these apps on your phone.
Instagram is designed for use on a phone, and as such, the website version of it is kind of clunky. It's completely usable, but you don't get sucked into the vortex of bullshit content like you do on a phone.
I find this idea much easier to implement than complete social media abstinence, and this actually removes the worst parts of social media - the endless scrolling, the notifications, the "stories", whilst still letting you keep up with friends, zone out for 30min in the evening etc.
Yoga/Weightlifting
Excersising is common external advice when you're struggling with depression. It's good advice, but it's hard to follow in the moment. I've found that yoga is the easiest way to move your body, and 15min works pretty well for resetting your mood.
On the other side of the coin is weightlifting - i'm a larger guy, and weightlifting gives the satisfaction of working out without the need for a lean body or a high level of cardiovascular fitness. It's quite a male stereotype, but to me it does seem like there is an element of truth to the idea that lifting heavy things makes you feel better. Some goals in weightlifting are quite easy to achieve regardless of your starting point (for example, deadlifting your bodyweight, or squatting your bodyweight), and they are in such raw units of measurement that they are quite satisfying to achieve.
Identifying delayed decisions
A key symptom of my depression is delayed decision making. I believe this is common, as one of the general symptoms of depression is over-indexing on the quality of present experiences relative to future experiences, which makes decision making difficult.
One specific example of this: when I first moved to the US, I wasn't sure if I was going to stay long term - so I didn't buy a bicycle, because I wouldn't have been able to take it back to the UK with me had I left. This is quite a bad decision! I love riding bikes; when I eventually bought one, I both enjoyed riding it, and it expanded my transportation options, which in turn improved my social life.
Identifying these decisions is hard, because inevitably they are closely tied to your personal circumstances, and often tied to underlying causes or triggers for depression. I now try to actively identify these decisions where I feel like I am being irrational, and ask for help to resolve them.