The majority of the time, a "failed alternator" means the voltage regulator died or wore out. The regulator typically has carbon brushes which wear over time/miles. Most of the time, the regulator can be replaced separately, but repair shops like to replace the entire alternator instead. The only other item on the alternator which is likely to fail are the bearings, which are usually also replaceable separately, but with much more effort required than swapping the regulator.
Disclaimer: I have quite a bit of experience with Bosch alternators from the 80's through early 2000's, but have no direct experience with the LR4 alternator. It appears the unit for most V8 LR4's is made by Denso, p/n LR065246 (previously LR023421), photo attached.
Interestingly, it appears the regulator is not available separately for the LR4 V8 alternator, or at least I could not find a part number in Microcat or via Google. Probably have to replace the entire assembly, spendy at the dealer ($901 list, ~$780 from discount dealers) but thankfully the aftermarket Denso is available for under $350:
https://importecautoparts.com/parts/part_number/LR065246