Do you have a meter? If you feel lightheaded and unsteady you might be experiencing a false hypo (Feels exactly like one, just doesn't have the numbers to back it up. If that's the case, have some protein. They'll go away as your body gets used to numbers in the normal range). On the other hand, the fatigue/muscle weakness could be due to the metformin, as it is known to cause vitamin B12 deficiency. Get some supplements and see whether that helps, should getting a test done for it through the GP mean jumping through too many covid-related hoops.
I'd say, keep at it with the low carb and exercize, maybe incorporate intermittent fasting if you haven't already. While metformin does reduce hunger, going low carb/high fat also does that, so who knows what is causing the reduced appetite? If they both are, you might not need the met as a crutch.And, well... Metformin can cause anxiety and depression so... Nothing to lose by putting your bets on low carb and exercize and see how you fare. Give it a few weeks or months. Your meter'll tell you how it's working for you.
Good luck,
Jo