I don't know what sparks joy in you but I'll tell you what I did. Went travelling by myself for 6 weeks and spent pretty much all of that time by myself. I called it banishing myself to go spend time with me. I went to places that weren't social, hiking, things where being alone adds to the adventure rather than leaving something missing. I started to create my experience and it can be as good or as bad as I imagine it.
Then there's things I want to do like study, learn an instrument, and a language, draw, all these things, another person would just get in the way. These are things to be done alone. When you have everything you need there is nothing missing, because lonely is the sense of something missing. Maybe ask yourself what that is and create it yourself, you can do it it just takes some self discovery and its been one of my favourite lessons of life