"Then find another job, when you're in a better mood this experience will go much better."
I am usually in a great mood when posting for jobs. It means I get a new opportunity and can learn new things.
"Catch their manager walking by and invite them in for coffee, when they see the cross-team communication and camaraderie they'll think it's the best thing ever, especially as it is self-formed and not HR-driven drivel."
I used to do this in the office, but it is a little more difficult when WFH. I do try to strike up some non-work conversation when I find out a personal fact about someone else, like a shared interest.
Thanks for all the input!
How to deal with it: Make life about everything outside of work. Work is an 8-hour day, if it's longer do things necessary to get it back down to 8 hours or less. After work, live your life. Do not "live for the weekend", it is a miserable way to be because there are 5 days you end up suffering through every week when every evening after work could become a joy. Friendship, romance, hobbies, exercise, put those into the weeknights and live the way you want to live (other than the 8-hour workday).
Then find another job, when you're in a better mood this experience will go much better. Also consider therapy. You may not be clinically depressed or suffering from anxiety like I was, but good therapists can help you develop strategies to cope with negative thoughts and experiences, as well as strategies that help you move beyond them.
While still in the undesirable job, find a way to make it more comfortable. My friends and I started an espresso club, meeting up twice a day during our 15-minute breaks that are legally required in the US. A manager complains about it? Catch their manager walking by and invite them in for coffee, when they see the cross-team communication and camaraderie they'll think it's the best thing ever, especially as it is self-formed and not HR-driven drivel. Those moments gave us chances to break free from the tedium and socialize in a positive way, connecting with people on teams we normally wouldn't interact with. Occasionally solving problems for each other that would've remained unsolved for weeks or months otherwise (which itself helps with work, a sense of accomplishment when the regular work seems hopelessly dull or pointless more days than not).