@Goodiewhemper don't worry too much about the exercise, and post virus it is really important to take it easy and build up gradually. Walking, swimming, gentle stretches... I read that exercise is great for toning, but makes a much smaller contribution to weight loss. What and how you eat is the main thing.
@MrsL81 sorry I can't answer your question, and sorry to hear about your long-covid. I think the general benefits of this way of eating are the empahsis on lots of veg, drinking lots of water and eating food that is not over processed. If you have enough energy try making some of the delicious recipies suggested on the recipe threads. Most of them can be made in large batches and frozen, so you can have them when you're feeling less well.
The variety of vegetables, and unprocessed meat/fish will provide essential nutrients, and the nuts, seeds, oils will give you energy. And eating no refined sugar, less alcohol and fewer processed carbs can only be good (for everyone).
You might also find you benefit from the support and encouragement on here, rather than feeling alone in your approach.
I'm not qualified to give nutitional advice but if I were you I'd try starting stright on bootcamp lite, so including nuts, seeds and some berries. I would also plan at least one meal a week that includes some pulses - lentils, beans, peas... I assume that establishing and maintaining a healthy gut biome would be one of your aims. I'm sure that does happen on the low carb regime but if your immune system is still low then pulses are a good way to add a boost.
I'd suggest three proper meals a day, plus snacks (since you don't want to loose weight).
For example:
B - low carb granola (rose Elliot's recipe is lovely) with full fat greek yogurt and a few raspberries
Snack - vegetable sticks with avocado dip
L - salmon fillet with buttery spinach and buttered cabbage
Snack - a mini cheese and almond muffin spread with low carb peanut butter
D - a lovely vibrant coulourful salad with your favourite protein (egg, mayonnaise, low carb coronation chicken etc). Dress you salad with olive oil / herb vinegrette or mayonnaise