“When fresh spinach sits during transportation over long distances or stays in your refrigerator for a week, its folate content drops so much that frozen spinach becomes the better source,” Mary Ellen Phipps, MPH, RDN, LD, wrote for CNBC in 2022.
This is because frozen spinach often goes through a flash-freezing process just hours after it has been harvested, which helps to lock more of its nutrients in. “One cup of frozen spinach has more than four times the amount of nutrients, including iron, vitamin C, and calcium, compared to a cup of fresh spinach,” adds Phipps.
Fresh is Best? Not Always When It Comes to Spinach — https://vegnews.com/vegan-health-wellness/best-form-of-spinach
I was super proud of myself this past week when I bought a clam-shell of organic spinach and ate the entire tub. Now I know I would have been better off nutritionally with one of the many packages of frozen spinach in my freezer.
Guess I should make my world famous Potato Crusted Spinach Quiche more often.
garyskitchen.net 
How about canned spinach? I buy Delmonte leaf spinach no salt added in the can and I actually eat a half can per day.
https://www.thedailymeal.com/1325889/why-frozen-spinach-better-long-lasting-canned-fresh/
It’s hard to find the no salt added variety. But the Publix I go to thankfully has it and of course they stock it on the very lowest shelf weigh in back. I think I’m the only person that buys it. But I do get about 10 cans every other week. I think I’m also the only person that buys the no salt cottage cheese. I buy three containers of that every week.