The 2021 and onward Bikes have the battery behind the front lights. I guess it shouldn't be too difficult to convert.
As for your battery, it's probably just old and dead. My lithium batteries did have the same symptoms on my KTM. The battery still works in my kickstart only street bike but will not start the KTM reliably. New battery fixed this.
My TRS is from 2019 with a starter btw but has still the original battery. But until I bought it a couple of months ago it had only 5h on it.