OP, learn to play an instrument! I started playing the recorder to help out my son when he started learning it at primary school - now I’m pretty good and we have loads of fun playing music together.
Also, when you’re a decent level, you can join a group / band / ensemble, which is a brilliant social thing. And it’s good for your brain too. Practising to get to a decent level takes time, so that’s at least an hour a day sorted.
Or join a local choir. Will be tricky to find one that practices in the day rather than evening, but you can always try.
Or learn a language. That’s great for your brain and a future career as well.
Or take up calligraphy - a few instuction books and pens don’t have to be expensive. It’s fun and can be turned into a money-making hobby if you start making personalised cards and sell them off on Etsy.
Or start writing a diary, make a scrapbook, get your kids’ art together and make something lovely out of it.
Or read all of the The Song of Ice and Fire. Don’t buy it, the local library will have it. It will take ages to get through that.
Or write a story and publish it on FanFiction website.
Watch lots of movies, classic and new. Watch all the hundreds of episodes of Doctor Who, currently a available for free on BBC iPlayer. Hundreds of hours usefully spent 😁 and kids will be awed when you introduce them to it.
Or start a business where people send you their and their kids’ second-hand clothes and you list and sell them on eBay, keeping a percentage of the price they sold for. It takes bloody ages and does mean extra cash.
For anything you need but can’t afford try Freecycle. People keep getting rid of amazing stuff all the time.
I have no time for myself at all, what with working part-time and looking after three school-age kids by myself, so I’m so jealous of your situation. If I could relieve you of some of your free time it would be bliss!
Good luck, and let us know if you’ve taken up some of the ideas on this thread.