Is there really no way to do this?
The iPads have had the hardware in the M-series chips and the software in the form of Apple's hypervisor framework in iPadOS for a couple of generations now, but Apple hasn't enabled it to be used officially.
I really wish they would just allow this on iPadOS. It still maintains the sandbox model Apple wants for iOS, it would just give a (contained) outlet for doing things that are difficult in native iPadOS.
In any case, Apple still wants to "review" apps, and we want (arbitrary) user code execution on device. That's something Apple strictly forbids on iOS/iPadOS AFAIK (which is why we can't even have Firefox addons). Unless we can have at least true side loading, a DMA extension to iPad won't help.
The DMA isn't really the right tool to liberate devices, since it's about market competition not consumer rights. I think it would be better to widely address this along right-to-repair, electronic waste reduction and consumer rights regarding actual ownership. Unconditionally locked hardware is ridiculous.
I wish they would simply unlock the bootloader, so we can have Asahi Linux for iPad. They don't have to do anything else. Although Asahi is on trajectory to exceed MacOS performance and dev usability, I don't think they would lose their existing appstore cattle to Linux, but rather gain new hardware only customers.
Though, I don't see true sideloading (like on Android) specified. If apps still need Apple's approval, we will get "freedom" who to pay, not what to run. I still don't see device liberation within the scope of the DMA.
However, if we're lucky, Apple may decide the app approval process may not be worth it, if they are not allowed to extort developers anymore, so they may allow unsupervised sideloading as a consequence.
In any case, requirements and reality may take much longer to align than 6 more months, considering Apple's cringeworthy tantrums so far...
But if Apple abuses its position as platform gatekeeper with the app approval process and rules, the EU will probably slap them down. The DMA doesn't care about device liberation, but it does care about fairness, so Apple will probably only be allowed to continue this if they act in very good faith towards 3rd parties, which doesn't seem like an Apple thing to do.
They removed the hypervisor framework in addition to the kernel support for virtualization a few months ago unfortunately.