A "keto" diet appears to be a more rigid/restrictive version of how I eat.... But For me (and many others on the forum) it is quite possible to eat this way long term.
I'm a fast approaching 81 year old T2 and I've eaten a very low carb/ketogenic style diet since I was diagnosed at the end of November 2013. To start with I simply cut out all the obvious high carb foods (I wasn't aware of the existence of glucose meters at first!) and my glucose levels came down from my diagnostic HbA1cs of 60-61 to pre-diabetic levels within 3 months, and they've generally remained at lower pre-diabetic levels since then, and without my needing diabetic meds since 2017. During those first few months I also lost around (a much needed) 20 kilos without trying, and have more recently lost another 10 kilos or so.
I limit my carbs to a maximum of 50g a day but often eat a lot less, sometimes more, and I regularly skip breakfast and very rarely snack. I use my meter, and for a while also used the original Libre 1 sensors, to check glucose and ketone levels/patterns, and those results are a guide to how I'm responding to various types/quantities of carbs. (My Libre reader can also act as both a glucose or ketone meter using appropriate test strips.)
I work on the basis that I require a fairly stable amount protein for my body's maintenance and repair, and then I do a balancing act with carbs and both dietary and body fats as fuel for energy. I believe that we are naturally dual fuel burners and for me my diet basically ensures that for most of the time I'm using fats/ketones as fuel instead of carbs/glucose, and my brain also definitely works best with ketones as its major fuel.
ETA : I believe it was eating too many carbs for several years that in part triggered my T2 and being able justify cutting them right back down has greatly improved my health. I've always eaten normal full fat food, so I never really had to deal with low carb / keto "flu" symptoms.