Probably named after Prince Félix (1893–1970), Grand Duchess Charlotte's husband.
Félix of Bourbon-Parma married his cousin Grand Duchess Charlotte in 1919 and became Prince of Luxembourg. In 1942 he left Canada for Britain with their eldest son, the future Grand Duke Jean, to join the army; on 10 September 1944 the two entered Luxembourg with the US 5th Armored Division. We have not yet found a record of when the boulevard was named, or for which Prince Félix.