Start small, with things that don't require any preparation or commitment. Go walk a bit, aimlessly. It's a difficult time for you and you might simply need to back off for a bit. Eat well, sleep, exercise.

Definitely avoid any social media, youtube, etc. I'd suggest to limit your screen usage to just your work-life. You do not want to compare yourself with people who are not in your position. Spending time on the internet is not fulfulling.

Once you have a healthy daily routine down (which you might have already), a lifehack is to challenge yourself to get good at something that you would never have imagined yourself doing. The idea is that you will fill your head with thoughts about how to improve, rather than thinking about other things which might be too much to process right now. This is why the "start lifting" suggestions work. You don't have to lift, but simply set some random goal. Avoid trying to achieve some big ambition that you've always had.

Once you're on this path, with time you will recalibrate. It seems you are a social person and I bet you will find other people to connect with.

From my own experience, switching from a remote job to an in-office job helped when I felt too isolated. The job market is tough (from what I've heard), so you can check if you could join a coworking space or simply go to the local library to work. I've had friends that are happy to just work together in the same space.

The point of my response is not to tell you "how to be alone", but helpful advice if you want to make changes to your life, if you are unsatisfied with it. If you are unhappy, you could fill all your time thinking about how unhappy you are. It's not helpful, though. For now, find ways to fill your time, and while you do that, I truly believe you will find your footing again.