I do sympathise with you OP. In my teens and twenties I had a wild social life, and a good circle of new friends at the start of my thirties through work and going out to a regular nightclub event for a particular genre of music. I never intended to lose contact with all of them, but did (some I was happy to in the end!).
It's a combination of kids, FT work (so no play dates with other mums) and moving further away and not being keen on driving that has caused this. My last circle of friends were all Europeans who went home (thanks Brexit for that, although I think the UK deteriorating was the main reason) , so I have one friend I've known my whole life and a couple of others who I mainly contact through WhatsApp. I rarely see them in the flesh. I've avoided Facebook as I hate most type of SM. I just wanted you to know that even people who have a great social life in the past can find themselves without many friends.
I do feel pretty lonely as I WFH too, but I actually feel like I don't have much room for friendships in my life at the moment as it's another thing to maintain, but I did wonder the other day how the hell I went from having loads of friends to hardly any! I used to work in a social job, which plugged the hole a bit for a while, so that might be an option for you. Stupidly I've had people ask me to go out, but as I've been breastfeeding for years I have turned it down so I can get my kids to sleep, so all this is partly my own fault.
I think meeting people through a common interest is easier, or if you can manage to have some time to yourself, volunteering for a charity might be good. You will always find overbearing characters everywhere, but generally people interested in a hobby or helping over people tend to be quite accepting, even if you are shy.
If you are struggling to find a hobby, look back to your past and what you excelled in or had interests in and start reading up on it or practice the skill at home, so it's less daunting around other people. Maybe go to a group with loads of older people first. They are usually very accepting and chatty, and you can practice initiating conversation with them.