I retired almost 2 years ago. I had a wonderful summer gardening, and was looking forward to a great winter skiing, when the pandemic shut down ski season. This was awful. I didn't have enough to do. To make it worse, I left a failing relationship and moved hours away to live near my daughter and family, who needed some help during the pandemic. In November. To a small city where everything was closed and I knew nobody but my daughter, her husband, and toddler granddaughter.
This spring brought improvement. I got a part-time job at a garden center, since I had no garden any more. Now I have a part-time job at a ski shop. I joined the ski club. I'm taking an online course. I'm in the process of joining a gym, and well before this started working harder on fitness. I'm trying to find volunteer work that will work out for my schedule and interests.
This is an incredibly difficult transition. I miss the social status I had in my job - I had a lot of respect and knew many people in my professional role. Learning to spend my savings (while I put off taking SS for two more years) has been difficult. Many others find it difficult as well.
For me, little p/t jobs (~12 hours/week) have been a godsend. I'm less likely to flake out than I might in volunteer work. I get up early, prepare, and enjoy the heck out of having coworkers and new friends. I like working hard. It has given me some structure that helps me manage my week better. And of course, getting out and meeting a friend for lunch on a restaurant patio is sure better than staying in an apartment.
I know the pandemic exacerbated my difficulty adjusting. But it would have been somewhat difficult anyway. Despite cutting down to 3 days/week for a couple years before retiring, I wasn't quite ready for completely unstructured time.
Best of luck! Don't fret if it takes awhile. Don't bury yourself in TV or internet. Get outdoors as much as possible. Find something meaningful to do with at least some of your time. It gets better!