I lost 3 stone during lockdown and have kept it off without difficulty since.
I was post menopausal, had put in a lot of weight sitting at my desk at work etc, and determined at the start of COVID that being a healthier weight and eating healthily were things that I could do something about to try and keep the worst effects of early Covid at bay (obesity was a significant risk factor for survival ).
What made it easier to lose and easy to maintain is that I didn’t ‘go on a diet’. I decided to nurture myself by eating more healthily , and to see that as a positive thing. Rather than blaming myself and hating my body and putting myself on a punishing regime.
I ate a breakfast that I enjoyed (frozen berries, Greek yog, a couple of spoons of granola)
Lunch: One slice of toast, some protein (not cheese, unless cottage) such as lean meat, chicken, tinned sardines, tuna, chicken peas salad) and salad / veg (not with mayo). Or I had lentil soup or similar with one slice of wholemeal toast.
Afternoon snack: (had healthy snacks at the ready to avoid raiding the biscuits) e.g 2 oatcakes and 30g brie and a satsuma. Or Two Nairn’s Oat Ginger biscuits and a glass of milk
Dinner: normal dinner but reduced the carbs portion and upped the veg. Maintained common sense and didn’t eat deep fried food regularly etc.
Cut out alcohol except for Fri and Sat.
Grabbed carrot sticks or cherry tomatoes if I felt like it.
I did eat cake at parties, have dark choc if I fancied it, etc .
If I didn’t lose during a week or even put a bit back on I just shrugged, took motivation from my overall success so far and carried on.
It was a little bit hard for the first 3 days because I was used to lots of sugar and constant toast making. And wine (a glass or two) most nights
But I adjusted very quickly , lost about 1 or 1 and a half pounds a week and felt great.
Now I follow the same pattern, but also have a bag of crisps (the ones from multi packs) or an ice cream (Solero at less than 100 Cals rather than nearly 300 Cals for a Magnum, but that’s ok and a new preference, I have lost my taste for constant rich sweet food) if I fancy it.
I did do a bit of measuring at the outset, just to reset my idea of what a portion of pasta or rice is. (Answer: less than was routinely doled out in our household of growing active teen boys!)
But for me, eating normal foods in a normal way was key to both weight loss and maintenance.
Good luck OP, with whatever works best for you.