I live 250 km from my family - in the same country but nothing like daily interaction. I have family who are transatlantic so I know how difficult the time zones can make communicating generally. My friends were all work colleagues or very distant physically, so I was quite alone initially during the week. And add in lockdown so many of the "normal" activities for new mums are not available.
I found the first while hard, very hard. I made myself go out and walk with DD in the pram every day - I had got one with a good rain cover and I had a decent rain coat, so I would go out no matter the weather and that did help just to get me moving and to get fresh air. I would often try to get as far as a local coffee shop, stop for a coffee and a feed, and then walk home again, to break up the day.
Being the "milk cow" is also hard (and DD had reflux, so threw up almost as much milk as she drank, and needed to be kept upright for half an hour after every feed to try and help that). I tried to time certain feeds to be able to watch an interesting programme on tv (it was the 1st year of the Great British Menu, if I remember right - but I know there was a cookery programme in the early evening that I watched a LOT), and I kept a book of sudokus on the side to do while DD fed at other times. I also had a travel mug, that I filled with a nice cup of tea (and had a stack of 3 fig rolls alongside) and a pint glass of squash to drink, to keep my own fluids up and to not "just" be the cow, but able to enjoy my own quiet cup of tea without it spilling and keeping it warm.
It does get better - newborns are so dependent on you, and while they still are dependent on you in many ways for years to come, it changes and they can do things for themselves or be more mobile and flexible, as they get older. And the country will open up again so activities and groups will restart at some point - maybe your health visitor or GP might have some pointers on where to look.
DD is now 14, the same height as me, and headed off walking down the same hill to her sailing camp this morning independent of me, and is cooking family dinner tonight while DH and I are still working upstairs. And I have a lot more friends locally, many of whom I met through activities or school etc for DD.