Never owned one. Had an 89 LC FJ62 that was bullet proof. But, I've done alot of research lately on LR4's and RR's, etc. Several googles will tell you best model years to consider, and worst model years for reliability and sepcific issues. TYpically, the drive train is solid, but cost cutters like colling system, air suspension compents, plastic timing chain guides in certain years of 5.0 V8's etc., are easy to find and decide if they have been addressed. The newer models mostly deal with crappy software bugs that have to be updated repeatedly to get vehicle functional. Early releases of the latest Defender ('21 and prior) had unexplained windshield cracking. THe biggest knock on current Defenders and LR's in general is software issues that disable the vehicles.
THe best LR4's are 2012-2013 where the timing chain guides and such supposedly went back to metal on the V8. THe LR4 basically had a double chassis which is why they are heavy, bomb proof. Also made them thirsty if you are towing anything heavier than a feather. Also made the front control arms and bushing wear out about every 50K cause they used oil filled bushings instead of rigid bushings. Spending a few hundred on control ar and bushing upgrades up front will resolve that (There's a LR specialzed parts supplier that starts with an 'M' that is the proper control arm and air suspension component supplier for upgrades. Can't remember full name off hand). As well as upgrading the air susension components on most models will cure any of those issues. Also upgrading cooling system components much like you'd be wise to do an a BMW.
Software issues might be less on say a 2019 RR before those new super sized interactive screens came out. And you can get low mileage 2019 RR's in mostly in the 30-50 range depending on appointments.
Just make sure you have a useable budget. A RR tail light assembly may set you back $1500. But a few quality part upgrades upfront could save alot down the road and you can make it a vehicle LR should have already done for what they cost new. THe good news for the used LR customer is that you can get one 3-4 years old for pennies on the dollar, spend 5-10K on upgrades and fixes and have a heck of a low mileage LR/RR for less than 50K if you do your homework and buy right. And in the case of an LR4 you can do that and be all in on a 60K mile car for under 30g. For LR4/Disco's I'd stick to 2012-13 V8 and use the savings after all in gudget for the gas station.
However, center and rear diff lock is mostly standard on all RR's. LR4 has to be the Lux HD package to get that when you are searching for one. If that's a requirement.