The Online Safety Act has to be understood as a regulation of the Big Tech platforms that form what we might call the NormieNet. Your web page is unlikely to come to the attention of politicians, Ofcom (the relevant regulator) or the wider public, so you almost certainly would not suffer any adverse consequences, even if you were a resident of the UK.
Britain has a long history of libertarianism - it's where American libertarianism came from - but British libertarians don't make florid speeches about how free they are, they just quietly do whatever it is they want to do without telling anyone who might object. During the coronavirus pandemic, the UK had particularly strict lockdown regulations, because the Johnson government believed that most people wouldn't take any notice of them.
I'm sure someone will come along soon to tell me that this is a terrible principle on which to run a country, but the truth is that Britain is governed entirely by realpolitik, because the historical record shows that strongly principled government does not endure[1].
Just need to come up with something to put on the page.
If Ofcom does decide to pursue you, they will start by asking to see your risk assessments and policy documents, and would then in theory proceed to legal action, but in practice would just ignore you, because you're just protesting, and they have no chance of getting the millions in fines out of you.
I'm not sure what content you could put on your page, but if anyone suggests a message of support for a protest group called Palestine Action, I most strongly recommend that you don't do this, because the nature of their protests has led to their proscription as a terrorist organisation, and the resultant legal action against you would be of a very different nature.
Starting with less extreme content, such as a how to buy drugs guide, and gradually escalating to provoke a response, would be wiser.