There are two parts to the European far right. One is the so-called "populist" right (a purposely misleading label, as their "populism" is just a mask for neoliberal and pro-corporate economic policies like tax cuts for the rich), which tends to be pro-Russia in most European countries because of their shared anti-liberal, socially conservative views (though not always... in Poland for instance the right wing is just as Russophobic as the liberal centrists are).
The other are the outright Neonazis who have ties to Ukraine's Neonazi scene and who are anti-Russian because they view the Russians as Asiatic non-Europeans and a threat to their vision of a racially pure Europe. The Ukrainian Neonazi movement has been busy over the past ten years building up connections with their counterparts in the rest of Europe, trafficking weapons and organizing para-military training camps.
They have had substantial resources to establish their networks in Europe thanks to state backing by the Kiev regime, and European governments have tolerated and turned a blind eye to these groups and their activities because of their usefulness against the Russians.
This latter group, from what i can tell, has never had a hugely positive view of Trump (in part also because of his ties to Jewish oligarchs) - though they of course welcomed his normalization of xenophobia and racism - and now if Trump ends up ditching the Ukraine project they may even turn outright hostile toward him.
I think unfortunately that both of these parts of the European right will be strengthened as a result of the Ukraine conflict. The first because it will have been validated in their skepticism toward the Ukraine project, and the second because there will be huge resentment in the Neonazi ranks over what they will perceive as the West's betrayal of their cause.
And that second group is especially concerning, as with the end of the war we will suddenly have a large number of hardcore ideological Nazis, with ample combat experience and severe PTSD, flood into Europe as Ukraine is either taken over by the Russians or is left as an economically devastated rump state where they will be unable to find jobs after the war.
Not to mention that the black market for all kinds of very dangerous weapons, which has already been thriving thanks to the monumental levels of corruption in Ukraine, will become an order of magnitude worse as tens of thousands of Ukrainian soldiers with no economic prospects and no war to fight anymore try to sell whatever they have left to whoever will buy it. In practice that means organized crime and militant Neonazi networks (these two often have significant overlap in Eastern Europe btw).