To extend your render distance far beyond the usual limits, you can use Distant Horizons, which creates LODs beyond your render distance to fake extreme distances of 512 and beyond, depending on your PC. DH also has some support for Iris on their Discord channel. Alternatively, you can use Bobby, which creates a cache of your chunks to extend your render distance. More accurate but more demanding. There is also Voxy, which creates accurate LODs based on areas you’ve already generated/visited, but is still in alpha and lacks a world generator like Distant Horizons.