The rule I have seen, and have followed is to target 1-2 lbs (about 0.5-1kg) per week. Any more than this and you start having issues where your skin doesn’t shrink at that same rate, or your body having issues baselining to the new weight[0]

Personally, while tough to keep that as an average weight, I was successful doing this, primarily by going to one meal a day, and limiting calories (especially carbohydrates). Only issue is your body does end up burning fat, which makes your feel a bit more “oily”.

[0] https://www.healthline.com/nutrition/losing-weight-too-fast

As with all guidelines, this always depends on the starting point and personal data.

If you are on the heavier side and a heavy drinker and carb eater, going low carb/no alcohol you will lose easily 10 kilos in a month (mostly being water weight).

If you are a healthy weight and eating normally with a glass of wine here and there, 0.5-1kg is probably a good range (and probably around 70% of it being fat loss)

If you are lean, 0.25-0.5kg a week is a good goal (and probably 50% will be fat).

No issues with gallstones. It was 230 lb to 185 lbs also at the start of the pandemic (May-July 2020). I have managed to mostly keep it off (currently 190, but have yo-yo’d back up to 200 once), despite resuming drinking and being a semi heavy drinker. Mostly due to diligence around keeping an OMAD style diet.