@CannondaleDad First of call, congratulations on getting to your goal weight!
Normally, the best recommendation for maintaining weight loss is to pretend it never happened. The pitfall of many is to diet hard, lose the weight, and then revert to old habits which puts the pounds back on. Habits around food and exercise are what determine weight, so a person with “200lbs habits” will be 200 lbs, and a person with “140lbs habits” will be 140 lbs. If a 200lbs person wants to be 140lbs, adopting the habits of someone already there (which will probably include eating less, moving more, opting for less calorie dense food, snacking less, etc) will lead to weight loss. However, your case is interesting, as the method you used to lose the weight (a ketogenic diet) is not actually a habit you wish to maintain moving forward (as I understand it).
Simply put, as long as you maintain a balance between intake and expenditure, you won’t regain the weight. This is news to no one, including you. Still, >80% of those that lose weight will not maintain it. Hunger is not fun, and willpower only gets you so far. What works for 6 months is not guaranteed to work for 6 years. A ketogenic diet works for many because it often reduces feelings of hunger due to a change in the ghrelin response. Typically, as a person loses weight, the body will upregulate ghrelin production accordingly. In other words, the more weight you lose, the hungrier you become. A ketogenic diet has been shown to downregulate this ghrelin response during weight loss, which means that you don’t get exponentially more hungry as the pounds drop off. This is obviously beneficial for compliance in the long term.
For concrete advice, I would agree with @2DollarLegs. You probably have a good idea of your current maintenance calories, so make sure you don’t stray too far from that number. Implement carbohydrate during workouts in the beginning and observe what dose produces a beneficial response.
A carbohydrate-centric diet is optimal for high performance endurance athletes, I don’t think there are many doubts about it anymore. Can you perform on low carb? Absolutely. Is it optimal for the best possible performance? No - cycling is a glycolytic sport. However, you are not a pro, and you probably have a life outside of cycling. Just because you wish to fuel workouts again does not mean you diet has to be carbohydrate-centric. If a ketogenic diet keeps you satisfied, at your goal weight, and doesn’ feel restrictive, there is nothing that says you can’t keep doing it. You may not perform optimally on the bike, but maybe that isn’t the goal of riding either. There are ways of doing a ketogenic diet while still fuelling with some carbohydrate during exercise, too. Zach Bitter, a well-known ultra runner, has gone into depth on this topic many times. He follows a ketogenic approach during all times, but for more intense or really long sessions, he takes in some carbohydrate to supplement and aid performance. This is a perfectly valid approach if you feel that the diet you currently have is something you’re happy with.
To summarise, regardless of carbohydrate intake, energy balance will determine whether or not you maintain the weight loss. If you are tired of doing a ketogenic diet and wish to shift completely moving forward, you will be completely fine as long as you maintain energy balance. In this case, the normal tips apply. Eat satiating, whole foods whenever possible, and aim for 1g/lb bw of protein. However, if you enjoy a ketogenic diet, you don’t have to stop doing it just because you’re a cyclist. If it helps you maintain your weight and control hunger, maybe that is worth more than the top level performance you’re giving up on the bike. That goes for all diets in my opinion - whatever works for you is good. Whether you’re carnivore, vegan, keto, high-carb, fruitarian - if you like what you’re doing, if it makes you feel good, if it keeps you at a healthy bodyweight - keep doing it.
Best of luck moving forward, I hope you find a way of eating that suits your life both on and off the bike!
Please note that this is only my opinion. I do my best to not step on any toes, but if I did, know that it was not intentional.