I wish I could get rid of my phone, but I can't. it's too useful. What I did to use my phone less is:
* Set the screen to grayscale. I have a shortcut setup to toggle grayscale/color, so that I can view things like images/videos the friends send me, but I go straight back to grayscale afterwards. I found that I spent a lot less time on apps like Instagram when they're in grayscale.
* Set up time limits for apps. Android and iOS both have features for this. In addition, set it up so that you need to enter a PIN to go over the limit. This worked well for me for a bit, but I quickly became reflexive in going over the limit (even with a PIN!). Adding a little bit of friction to going over the limit gives me the chance to think and consider if I really want to be using my phone. So, don't memorize the PIN that you set -- write it down on a piece of paper and stick it between the back of your phone and your phone case. This adds some friction so that you don't reflexively go over your time limits -- if you _really_ need to use some app you can.
* Delete any apps that you don't actually need. For me, I deleted all social media apps, and basically anything I could access on my desktop/laptop. Go further, and really question what apps you need. Do you really need easy access to your email, or Discord, or Reddit, on your phone?
* If you're able to stomach it, delete your social media accounts. I did this last year, and I don't miss anything. I keep in touch with friends by texting them, asking to setup phone calls, and so on. I did like being able to see what's going on in my friend's lives, but I don't think it was worth the negative effects. If you want to keep in touch with people, you can do so without social media. Send postcards or letters to friends. Actually seek out talking to the people that you want to hear from, rather than passively posting/reading online.
* Consider your consumption of news like Reddit, Hacker News, news sites, and so on. I thought I needed Reddit. I thought that it added positive value. I spent a _lot_ of time on Reddit in college. But, after I graduated I slowly weaned myself off. Now I realize that it did have _some_ marginal benefit in keeping up with the news, but I think there was a giant negative impact. Reddit can be a very negative and cynical place; I think it can really influence your thoughts in ways you don't realize. I also saw that there are other ways to keep up with current (I now read the New York Times instead).
* Regarding Hacker News, take advantage of the noprocrast features. Also, I use hckr news [0] so that it only shows me the top 10 articles each day. This means I spend less time on here, but I still get the majority of the benefit of reading Hacker News.
Of course, you don't have to apply all of the above at once! According to iOS Screen Time, over the course of maybe ~2 years I went from using my phone 2.5-3 hours per day, to ~15 minutes per day now.
Hope that you find something that works for you! You (or anyone else!) feel free to email me if you need any advice. I'm certainly not an expert, but I'm so happy that I no longer reflexively pull out my phone.
* [0]: https://hckrnews.com/