With the release of 4000 series cards, the size of GPUs has increased significantly (almost comically in some cases) and 3+ slot cards now appear to be the norm.
The DA6 features support for a 3-slot bracket but the size of the card can extend beyond the bracket and to the edge of the case will accommodate cards that are 87mm thick (that is 4+ slots). If you dont mind the card sticking out beyond the edge of the case, then it’s possible to support cards thicker than 87mm.
The height of the card is limited to 143mm as it will then make contact with the PSU socket but this can be lowered (by removing the standoffs and then using an angled power cable to plug in) or removed entirely (by using a cable directly to the PSU) increasing that limit to 160mm.
The image below shows the DA6 XL which supports cards up to 368mm in length but the same width and height dimensions apply to the DA6 but with a shorter length of 323mm.