Was there ever an account of Jewish knights in high or late medieval Europe (anywhere from Normandy to Russia)?

If by Jewish knights you mean practicing religious Jews, then no. In most Christian European states, Jews did not partake in military services of any kind, a prohibition that went back to the Theodosian Code of 438 in the later Roman Empire. The Iberian kingdoms saw some important exceptions, and we hear of Jews fighting in the kings of Castille at the battle of Sagrajas in 1086 and at the siege of Cordoba in 1236, though not as knights. Indeed, we even find Jewish archers (ballasteros) being granted lands in Andalusia by the kings of Castile in the 1260s, and a Jewish mercenary called Abrahim commanded a group of Muslim jinetes in the service of the King of Aragon in the 14th century. The Iberian Peninsula arguably represented an important exception to the rule however - it was a highly militarised and religiously pluralist frontier society, so Jews would have had opportunities for military service that they otherwise would not have had in other parts of the Christian and Muslim worlds.

Its worth noting that chivalric culture was not exclusively Christian. The Church tried to assert a monopoly on the dubbing ceremony, but never succeeded, and though most Christian knights were very religious, they tended to see themselves as having a direct relationship with God rather than one mediated by the clerical hierarchy - see "The Book of Chivalry" of Geoffroi de Charny (a famous 14th century French knight", or Richard Kaeuper's "Holy Warriors: the Religious Ideology of Medieval Chivalry" (2008). And in the chivalric imagination, chivalry and knighthood didn't have to be an exclusively Christian thing. As early as the writings of Benoit de St Maure and Chretien de Troyes in the 12th century, it is clear that courtly poets believed that chivalry and knighthood, or at least parallels of them, had existed in pagan Greece and Rome. In the same century, Usamah ibn Munqidh, an Arab gentleman and warrior who wrote "The Book of Contemplation", recalled that King Fulk and the Frankish knights of the kingdom of Jerusalem identified him as a Muslim Arab "knight." A century later we find Jean de Joinville, a knight from Champagne, writing of "knights" existing in the pagan Mongol army of Genghis Khan. And by the early 15th century, when chivalry was becoming very much infused with early renaissance humanism, we find ancient Romans like Scipio Africanus, Pompey and Julius Caesar being held up as exemplars of chivalry to French knights, who were believed to be too lax in comparison to the rigorous standards of martial training and discipline of the ancient Romans. Never have I encountered Jews being identified as knights, but Jews seem to have taken up the implications of chivalric culture not being an exclusively Christian thing, as we find a large number of Hebrew and Yiddish chivalric romances - some of them are Arthurian ones like the Melekh Artus and Widiwilt (about Sir Gawain of Green knight fame, but with a stronger emphasis on love and marriage and a happier ending), as well as original ones like the romance of Maskil and Peninah. These are very important to remember, not least because they counter the stereotype of medieval European Jews as being all sober moneylenders, doctors and scholars.

Finally, when we look at Jews who converted to Christianity, we do find a few Jewish knights. Taking an example from towards the end of the period is that of Edward Brampton (1440 - 1508). Edward Brampton was born Duarte Brandano in Lisbon, the illegitimate son of a Jewish woman called Mariana. He then emigrated to England in the late 1450s and the future King Edward IV adopted him on condition that he converted to Catholicism. Edward pursued a highly successful career in royal service, fighting in various engagements in the Wars of the Roses including the battle of Tewkesbury in 1471, serving as governor of Guernsey and marrying an English noblewoman, Lady Margaret Brampton. In 1484, he was knighted by King Richard III of England, but after Richard was slain at Bosworth Field the following year he left for the Netherlands where he entered the court of Margaret of Burgundy, Edward IV's daughter and dowager duchess of Burgundy, and it was there that he seems to have spent the rest of his days.