After about 4 months on the diet, I found a local university sports lab that offered a metabolic efficiency test. You could do it either cycling or running. I was only cycling at the time so my choice was easy. Funny story, though, the guy giving the test was so surprised by the result (very high 50/50 crossover point), he said to me he thought the machine was broken. My max fat metabolism was 1.4g/min and my 50/50 crossover point was very close to my ftp. He later called me to say it worked for the rest of the tests that day so it must have been right for mine too.
If you can find one nearby, and you are trying to see if you are fat adapted, I recommend it. It isn’t pleasant, but the data is priceless if you’re doing a long distance event. You can get a good sense for your bonk point, assuming you are trained well for the distance.
If your thing is punchy climbs, I understand the data on anaerobic performance being more mixed on a high fat diet. There are some N of 1 people who seem to defy that (Dr. Shawn Baker, e.g.), but I admit to not have dived deep into that end of performance as I live in Flatland USA and my thing is triathlon, TTs, and flat training rides.