Edit: Bizarrely, my records show I DID just sell the game to someone, 3 days ago, in Poland, via Paypal. Maybe this is a one-off glitch and not more general policy?
First, thank you for your interest in the game.
Second, a lot has happened the past two or three months. It's all there in excruciating detail in my dev logs, but for a VERY summarized version:
1. A group of deranged upper-middle-class Australian women called Collective Shout started targeting some aggressive sexual games on steam, most directly "No Mercy". As they couldn't black mail steam into compliance, they instead contacted payment processors, and got them to force Steam to censor its service and remove titles. It was later discovered that this group had DEEP political ties: to the Australian government, payment processors, and various international groups bent on dictating to people how to live their lives. This was not a random activist group getting things taken down by sending a few complaint emails.
2. "No Mercy" was also on Itch. People flocked to Itch to support it. The deranged women caught wind of this and made the same cartel-like threats against Itch. In response Itch:
a. Hid ALL NSFW games from search/recommendations etc
b. Totally removed the specific games mentioned
c. Removed Stripe (ordinary credit card processing) from NSFW titles.
3. People got pissed and various counter-pressure responses were made: calling campaigns against Visa/MasterCard, info campaigns against Collective Shout on Twitter, etc. None of this had any effect (other than getting some Twitter accounts privated), because unlike the deranged women we have no under-the-table ties to governments, payment processors or shadowy global organizations.
4. A few weeks later Itch allowed FREE NSFW games back onto search, (but not onto recommendations) and claimed they were looking into alternatives to replace stripe.
5. It has now been nearly a month. No alternative payment processors have been added, and for-pay NSFW games are still banned from search. This is VERY BAD, as a recent poll demonstrated that 75% of discovery for my games was via Itch. I imagine the same is true for most similar games. At this point, it's looking like Itch may very well abandon NSFW titles entirely, either by fully banning them or just letting them rot in this shadowbanned state forever, which over time will be the same thing (new games won't come, old ones will shrivel up and die).
Third, I'm sorry to say this, but if you live in the EU, you no longer live in a free state. This is even more true for those in the UK. The US will follow soon, on its current course, but it's not quite there yet. Freedom of speech and expression is going away. The right to, or expectation of privacy is going away. The ability to actually OWN anything is going away. You not being able to buy a porn game is just a small symptom of a much larger leviathan that is now curling around the entire world, and beginning to squeeze. Do with that information what you will. Steam recently lost half of THEIR Paypal support too. Not for NSFW titles, just across the board. The bank servicing it just left, no explanation given, no demands made. A whole bunch of currencies just nuked.
But maybe you don't care about any of that. To answer your question directly, there is currently one way: Join the SubscribeStar (https://subscribestar.adult/bitshift) for one month, $10, same as the cost of the game. I'll send you a key, you can cancel after the month is up. SubscribeStar uses payment processors designed for "high risk", so they're somewhat less vulnerable to what's going on right now. Whether your card, from Poland, will actually be able to be processed is anyone's guess though, because again, the level of financial censorship in Europe is being cranked higher and higher currently.