I don’t have data to quote here but considering heart problems were rare back in the day when butter, lard and tallow was used in generous amounts in combination with obesity being rare and daily labor was common, I would assume it would be mostly fine. Heart problems in non-overweight people are rare even today, especially at younger ages.

There are also 2 new high quality studies out there showing milk fats being significantly safer for heart health compared to other saturated animal fats. I can link that study for you on request. However you wouldn’t need to use butter for your potatoes necessarily. You can oven bake potatoes in rapeseed oil or olive oil just fine and get the same calories in, if you happen to be afraid of milk fat that is. Finding a milk alternative would be harder however since the seed and nut oils out there are generally much less nutrient dense than whole milk. The exception would be soy milk but then you have to be careful not to get a version full of sugar.

When trying to gain weight (or simply not go minus as in your case) the method will be the opposite of what is needed to lose weight. I have helped someone with this in the past and what I saw as his greatest trouble was that he would get too full to eat more very quickly. I asked about his diet and it was just full of foods which are very filling without actually containing many calories. Lots of fruits and vegetables with almost no carb and no fat.

So really what you need are easily digestible and not too filling calorie rich ingredients. Think lots of grains and fat. Buttered potatoes instead of air fried potatoes. Carrots instead of lettuce. White pasta over whole grain pasta. Cream or mayo based sauce instead of a stock/water based sauce etc. However still try to eat healthy. If going for bread take the white bread without added sugar for example. And still include vegetables but don’t make them over ⅓ of your plate. I have read many success stories with adding heavy amounts of dairy to the diet which makes sense since milk is there to grow a calf as fast as possible. Drinking a package of milk a day is almost a miracle cure to being underweight if you can stomach it. In fact the medical food packs they give to malnourished children are dairy based. Consider it if your diet allows it.

However what specific meals which are convenient to bring I don’t have many ideas. But I hope this mode of thinking will help at least a bit. It has to be a big portion that you can actually stomach. Think about which foods you seem to be able to eat a huge amount of and then narrow those down to the most calorie rich. They also have to not clog your stomach for the whole rest of the day so being easy to digest is also key.

I have not used either for cars but I have tried both for driving bicycles. The thing with open street map is that they have a lot more of the small streets that bikes can go on but cars can’t. In my experience google maps usually wants me to drive my bike right on some huge multi-lane car road for 3 hours and totally ignores the bike path right next to it. When I went on a 1 month bicycling trip I tried both but found that OSMAnd had vastly better suited roads. Some of the tiniest tiny roads it sent me on were some of the most memorable of the whole journey. Sometimes the path in OSMAnd will just be a dirt path half a meter wide and I love that. I thought many times who on earth even added all these roads! I’m so thankful for every local nerd who added every single dirt road in his neighborhood on there. Simply amazing sometimes. But yeah it doesn’t work at all if you don’t download the map that’s true. Also I really can’t answer for navigating by car.

I’m afraid that AI doesn’t have to be better than human beings at a certain task for them to replace humans. AI just has to be good enough. Humans are insanely expensive to pay so even if a AI will do a much worse job but still acceptable then companies may still want to replace those workers. I’m afraid that AI will just make products and services just slightly more shitty just for the sake of corporate profits.