Been in the same situation but without the work, so 5 days on the trot with the kids and no husband.
Some ideas, but I’ve only read your posts so maybe these have been said;
Most other mums I know either work full time or different days to me. - so you need to meet new people then.
Find a way to do something by yourself. Fri/sat/sun night. Sat morning. Sun morning. Whatever, when DH is home, think of something you would enjoy and is social and do it. From my lens, a choir is amazing for this - loads of socialising, splinter groups, travel etc BUT not for everyone and often not the right age range for a young mum so hopefully you can find something that you would enjoy doing for you that is social (eg not running). Very hard to think of let alone find, hence you’re in the situation you’re in!
Join/start a nursery WhatsApp to arrange play dates with the little one’s friends. Technically not allowed at our nursery but we have one anyway. Someone started it up by grabbing people at drop off/pick up (I never see anyone but somehow she got me one day) and it’s grown, so I’ve been able to get DD’s bestie round for a play and a park trip and her mum is really nice so potential social interaction there.
Similar, my friend created a neighbourhood mums WhatsApp - added a couple of people she did know, everyone was able to add people, and now there’s 100+ mums on a chat.
Sounds absolutely horrendous, yes, BUT your problem is that you’re lonely. This is proving a good way to hear about events, classes, meet ups that otherwise I somehow wouldn’t, and have general day to day chat with others. It’s like a mini mumsnet, lots of people asking parenting and life advice. And it’s not constant drivel. Takes the edge off the isolation.
Online clubs? I’ve joined an album club lately, so like a book club but for music. Again not great as not in person. Art club/course, book clubs…..
Main advice is to know that it’s a phase. When your youngest goes to school you’re gonna have 3 days to do whatever the hell you want (and so you should, make sure you don’t rush to increase your days. Even a year with that set up would be glorious!).
Also know that not everyone has to be an actual friend. Things can keep you ticking over socially for the time being.