Hi OP,
When you are obese, the holy grail to losing weight is a calorie deficit. There are no magic solutions and, having been in your shoes, my advice would be don't over-complicate things.
The reason we are obese is that we eat too many calories.
The good news is that if you are obese, you can still have a calorie deficit with quite a high calorie intake.
As you worked well with a PT before, might a coach work for you? There are loads of online ones these days (though do your research carefully, some are a bit cultish, some are cowboys, some are dangerous... ).
My numbers are eerily like yours, it almost could be me except I started at half a kilo left and am late 30s so a couple of years older. I have been overweight pretty much all my life, have suffered with eating disorders since I was 15, got quite successful losing weight once or twice through a couple of plans like WW or just plain calorie counting. But it was always short lived because I didn't address how I would actually live like this forever.
The pandemic ruined me in many ways and I've hovered around 15 stone for several years. I tried a fitness coach who I was working well with and making progress, but I was on 1200 calories a day and he tried to cut it to 1100 (I refused). I wasn't hungry on 1200, I ate well and planned well, felt energetic etc, but it was very inflexible. This was in lockdown so nothing else to focus on but ways to stretch 1200 calories. My coach then got ill and stopped working. My life also went tits up and I ended up quitting and gaining everything back.
I tried another coach a year later but we didn't gel. However, he put me on 1700 calories to start, and I was losing quite steadily so I thought OK maybe I can be a bit more flexible. I ditched the coach and had many failed attempts at just going it alone on anything between 1400-1700 calories.
I felt like a total failure and was full of self loathing, but then I tried to look back at the positives of every failed attempt.
It turned I was successful when I ate food I liked, and did exercise I liked. Simple. I'm reasonably active, I have an active hobby and hit 12000 steps most days (a couple of days a week I get to 18-20000 and it doesn't feel exhausting). So the missing pieces were focused high intensity exercise, and sorting out my atrocious diet.
I also realised I needed support, I don't have anyone around me who is supportive, so someone to help with structure and frustrations was needed. I decided to invest in an online fitness coach. People scoff and say it's expensive and you could just figure it out on your own, but I've been trying to do that for 40 years. There is no shame in needing help, but find the right help for you.
I found a new coach this year, by chance really. I wasn't planning on it but stumbled upon her company by chance, was sick of how I looked at the time, and everything she was saying made sense to me. So I just took the plunge. In a way I think that was key, because I didn't have time to put all these mental barriers in the way like "I'll do it after the weekend /my holiday /my busy period at work".
She's put me on 2000 calories a day to start. I thought this was mad, but I've been losing 0.5-1kg a week. Most days I eat about 1800 and am full - before, I could easily eat a packet of pasta meant for 2 people and an entire packet of chocolate digestives. Maybe it's psychological - knowing I have 2000 to play with means I don't feel like I've ruined everything if I eat over a tiny number by a tiny amount. It's also a bit more flexible if you have a meal out one day or whatever, just shave a couple of hundred calories from some other days that week.
2000 calories is also loads of food; you can be satisfied and nourished on 17-1800, and then if you fancy a Crunchie on the odd day it's not the end of the world. I eat normal food - eggs, whole milk, real butter, bread, meat, veg, potatoes ...I'm actually enjoying food again instead of feeling guilt and shame.
I'm also weight training, which is making a big difference, and is also fun and rewarding.
I'm sure the losses will plateau and I will need to drop the calories and up the workouts to still be in a deficit at some point, but I feel much more in control of my eating and am breaking the super restriction vs binge cycle. Things feel sustainable now.
If you are obsese, you are probably quite fixated on food, so things like one meal a day are unlikely to be sustainable, and are very likely to make you feel shit, off the wagon.
If you get down to ten stone and fancy dropping to 9 or 8, then maybe it's worth experimenting with other diet theories. But in your shoes I would stick with regular eating and a calorie deficit until stops working.