I live alone, have done so for years after my marriage ended and the children grew up. I absolutely love it, wouldn't have life any other way now.
What do I do with my alone time? All the normal things really. Every day I go shopping, clean the house, do the food shop, chill in front of a favourite programme on TV. I do my own painting and decorating so I'm often painting walls, or repainting a cupboard etc.
I'm quite crafty so I sew things (not very often!) but I do write...currently I'm trying to write my life story. I read a lot, mostly non-fiction...autobiographies and so on. I go for long walks down the country lanes, often 6 or 7 miles. I'm interested in nature and take my binoculars for bird watching. I have a sketch book and practise sketching....I also do watercolour painting.
For special times I go out, I am happy to go out for a meal alone but I almost always end up chatting to people. I meet with friends or (before COVID) would go round to a neighbours for a coffee and chat, it might be daytime or evening. I'd love to have a garden but currently I don't; however, I do help a friend with their garden, it's exercise, fun and good conversation. I am even happy to go on holiday alone but nearer home I will happily go for the day to see a place I haven't visited before (eg. York, Stratford etc.) and do the town centre, the museums and art galleries, the shops....
There are so many things to do alone...but they are all normal stuff. Why would it be different because someone is on their own? Research some crafts or hobbies you might be interested in taking up or, if you want to get out of the house, book weekend classes of some sort....art groups, salsa, exercise class or whatever....