Sideloading does not mean that you’re not subject to a ToS or that you will get full access to system frameworks.
This would potentially still require you to have an Apple developer membership to properly codesign binaries (like on macOS) if you distribute binaries and thus Apple could ask for financial audits to determine your income made with iOS customers.
This was explicitly mentioned in the court ruling: If a payment provider outside of Apple is used, Apple is entitled to such an audit to determine the size of the fee.
They might have to - while the DMA requires them to allow sideloading or alternative stores, the DSA requires them (and alternative stores) to govern the system and protect users as well as remove illegal and violating content (and the EUs level of free speech varies between member countries).
And even under the DMA ‘the gatekeeper shall not be prevented from taking … strictly necessary and proportionate measures to ensure that third-party [apps and app stores] do not endanger the integrity of the [gatekeeper's] hardware or operating system, provided such measures are duly justified by the gatekeeper’.
People seem to be grossly under-informed (or unfazed) about either regulation and also blissfully unaware of the muzzling of free speech and the amount of censorship provisions contained in the DSA.
It’s as if the EUs regulatory left hand does’t know what its right hand is doing. The EU has an almost naive belief in the ‘magical’ abilities of software companies to make opposing legal requirements work so they can have their cake and eat it too.