I bought the car in 2016 with 100k miles, no air suspension, it was taken off at some point and converted to coils and springs.

Year/Make/Model: 2008 range rover 4.4L V8 petrol w/ 179k miles

Problem: this issue with no start has began 5 1/2 months ago, it began when I took apart the dashboard and tried starting the car with the Touchscreen display disconnected, Passenger side Airbag disconnected, CD Changer and head unit module disconnected...I hooked up the battery charger to battery, but I didn't disconnect the power or ground. so yes, the battery was connected and I just charged it up while I worked. After I realized the car wasn't starting, I called mechanic and got recommendations. so I disconnected the battery power and ground while I put everything back together. Once I was done, I reconnected the battery, preformed a test procedure, locked the doors, opened the doors etc. got in vehicle put key in position II and tried starting and it started right up. next day got two starts before it began to not start again. towed to mechanic.

currently, I must jump to start it and transmission shifting issues present when jumped. also, backup camera won't work I guess bcs of the tie in to the canbus system. also battery drains with multiple jumps (could this be an alternator problem?) gas mileage poor too when transmission is immobilized like this

I am using a power probe to jump, I remove the starter relay in the engine box and send voltage to position 5 with the key in position II. I got the car back a month ago and have gotten the car to wakeup sometimes and start naturally and the backup camera works fine, transmission runs fine, but I only get a couple days at most before the car won't start again

Most repeated DTC: U0101 - Lost communication with TCM

land rover dealership replaced steering angle sensor and programmed/calibrated successfully
installed a jumper wire in engine box that i remove WHEN car starts-up. (which mechanic removed bcs it too was draining battery) dealership could not get their diagnostic computers to see my TCM
In the END all they could offer was quote of 22,000 for a NEW complete wire harness from end to end.
I declined and took the car, bill was $3,700 for the new steering angle sensor and jumper wire to get it to start lol

the mechanic, who i use most often tried installing a new valve body but claims it didn't work. also tried a steering lock bypass, neutral safety switch sensor repair, swapping transfer case module but nothing fixed the problem. starter was tested and he said it was good

Also, I have a faulty parking brake module which began before the NO start problem, It began after my brakes were installed almost a couple years ago.

On the instrument panel, when I insert key into position II I see the following messages

Parking brake fault
I see Transmission fault limited gears only
HDC Fault system not available

Please help with anything, it would be greatly appreciated.

I can potentially help with the parking brake fault. If the rear discs were replaced, the parking brake shoes are situated behind the disc - if not reinstalled (hopefully with all new parts) and set up correctly they can cause issues with the actuator/cable/general operation of the parking brake. I have seen this before when I worked on BMW X5's which shared the same type of system, some independant garages would replace the rear discs and not reinstall the parking brake assembly correctly and/or not follow the electronically controlled bedding in procedure. This would cause alot of issues and in some case damaged the EPB actuator which then had to be replaced.