Try go outside for exercise like walking, jogging or ride a bike if you have one by yourself. There is not much risk to get infected if you are outside and keeping away from a crowd doing that. Although it isn't a socialising based activity with others, it will help to clear your mind and get some health benefits from doing some cardio.
Also, yeah it can be tough to live inside for ages and not have any contact with your friends or other people. I didn't see my friends until early December for like over 7 months due to the earlier lockdown in 2021 because we all lived in a restricted LGA. However, during that time we still made efforts to keep in contact and try to be as positive during that time. One of the ways we did this was by talking daily on messenger or whatsapp in our group chat and also once or twice a week we would hold a games session on Zoom. We just played any random free games like the drawing and guessing ones, codenames, cards games. That way we still kept in contact and it reduced the feeling of just being alone by yourself.
Try to arrange that kind of stuff with your friends. Even if it's not a games session you can just like hold a video chat for an hour and talk about stuff.