In Germany, I understand that openly displaying Nazi symbols is illegal but that is heavily dependent on the context indicating that they are being displayed as a promotion or celebration of Nazism. So, for example, using a swastika in a Buddhist temple would not be an offence. (Related: Is it legal to display Buddhist/Hindu swastikas in Germany?) I assume in this case that using a symbol like the swastika to denounce Nazism (such as if it had an X though it to signify resistance and opposition to fascism), or to denounce something else by likening it to Nazism would also not fall foul of the relevant provisions.
In the U.K. there is the terrorism act which specifically forbids displaying support for specifically enumerated proscribed organisations, though I’m not personally aware of any Nazi organisations being on the relevant proscribed lists. And then there are the racial and religious hatred acts that created aggravated versions of various public order offences.
Communist Ranjeet Brar was today arrested for selling a book that condemns Zionism including by likening it with and drawing historical parallels of it to Nazism. Actually it denounces Zionism by arguing it to be itself antisemitic. And the book has a Star of David superimposed and integrated with a swastika, which anyone would hopefully be able to interpret the intended message of by giving it a brief moment of thought. Based on the cop’s remarks to bystanders challenging them on the grounds of the arrest, it seemed to be on the grounds of racially aggravated public order act offences, presumably that of section 5.
My personal feeling is that such a prosecution given the context and spirit of the use of the Nazi symbol will not hold up in court, or even likely make it to court, and further, that such an arrest would likely not have been done by police prior to the high level political gestures and machinations between Central government and police on the perceived need to further restrict free speech where it may be sent to verge on Antisemitism. It seems to me that this is likely to be a case of low level police constables simplistically and reflexively applying crude or heuristically crafted operational directives telling them to be on the look out for any anti semantic banners or symbols, because these can be argued to breach certain specific laws, and that it is simply a case of nuanced and rigorous understandings of the law not making it down the operational chain of command.
But the real question is what the case laws say about this: is the mere display of Nazi symbology which is not undertaken in a supportive or other genuinely Antisemitic spirit but perhaps liable to misunderstanding by less intelligent or less-than-sincere members of the public by itself enough to constitute an offence?