What did the Ottomans and Muslims think of the alliance with France ? Did it shocked them as much as the other European nations ?

I’ll try to answer your question, sorry if it doesn’t satisfy you

For now, we can see Ottoman perspectives of this alliance from two chronicles that included account of this event, the Tarih-i Feth-i Şikloş ve Estergon ve İstunibelgrad (History of the Conquest of Şikloş, Estergon and İstunibelgrad) by Nasuh Matrakçı and Gazavat-ı Hayreddin Paşa (The Exploits of Hayreddin Pasha) by Muradi. Matrakçı was a court historian and miniature painter who probably was a participant in 1543 campaign while Muradi is Hayreddin Barbarossa’s companion and he made use of informants who went on the campaign as well as Ottoman archival material in compiling his chronicle. Both people are not exactly the ‘common folk’ but I think they’re the ones that we have for now

Both accounts views alliance with France favourably. Matrakçı claimed that the Genoese had advised Charles V to renounce his claim to imperial authority and make an alliance with France, in order to oppose the Muslims. Thus, he agreed and understood that allying with François, which he views as a just ruler was necessary in preventing Christendom from uniting and threatening the Ottoman Empire. Matrakçı described François by including a letter supposedly written by François to Süleyman. This ‘letter’ doesn’t resemble any authentic letters written by François to Süleyman so most likely it’s just Matrakçı’s invention. In this letter, François was compared to the Sassanian ruler Khosrow I, who some Muslims considered the supreme example of royal justice. Thus François’s non-Muslim status was acknowledged while also emphasizing his greatness. When Matrakçı stated that François was a great infidel ruler, the term ‘infidel’ was not meant to be derogatory but merely to indicate that he was Christian. While Matrakcı considered François and his country France rich and prestigious, they needed the sultan’s aid against the Habsburgs.

Later Matrakçı recounted the history of Hasan, the Muslim ruler of Tunis who became an ally of Charles V. Hayreddin Pasha defeated Hasan and conquered Tunis, but then Hayreddin Pasha lost the city to Charles V who reinstated Hasan as its ruler. According to Matrakçı’s account, while Hasan was absent from Tunis supporting Charles V, Tunisian populace replaced him with his son, Ahmed. Hasan then attempted to regain control of Tunis with the support of Spanish mercenaries. Therefore, Ahmed asked the ulema of Tunis, “My father...allied with the lowly infidels. What is the divine command and the noble order of the prophet concerning it?” They gave him a fetva according to the hadith, ‘Whoever acts like a people is of them,’ allowing Ahmed to kill his father because of his betrayal of Islam. Matrakçı condemned Hasan, not because he allied with Charles V, but because his actions were harming Muslims. So by this logic, as long as the intention is not to harm fellow Muslims, allying with an infidel ruler is permissible. So in that respect, Süleyman allied with an infidel, the king of France, who was described as a just ruler. All infidels were not the same, as the kings of Spain were known for their cruelty and oppression against the Muslims of Spain. To ally with them, rulers infamous for the harm they caused Muslims, was altogether different from allying with the king of France, who was fighting the archenemy Spain. Also, at the time that Süleyman sent his fleet to aid François, he was fighting the Habsburgs in Hungary. The Ottomans also frequently had Christian allies while consolidating their power in Anatolia and the Balkans, but they used their alliances with Christians to further their ambitions, which to him improved the cause of the Muslim community. In addition, Muradi also recorded the benefits France gained from the alliance. With Ottoman support the French were more successful in fighting the war against Charles V because fear of an Ottoman attack had caused the Spanish to abandon most of the coast as many towns and fortresses submitted to the French or they were sacked. When Hayreddin informed the sultan of the reasons they should winter in Toulon, he stated that if they left, Andrea Doria would come with his galleys and harm French possessions, as he had before the Ottoman fleet arrived. The French needed the Ottoman fleet to protect the Mediterranean coast of France from Habsburg invasions

Though with that said, later Ottoman historians have more amusing explanation about the uncommon alliance between France and the Ottomans, blood ties. Ibrahim Peçevi almost a century later reports in great length the myth of the “French princess”. According to him, during Murad II’s reign, corsairs had seized a ship carrying the daughter of the King of France. Being brought into the Ottoman harem, she had then given birth to Murad’s most prominent son, Mehmed II. This, according to Peçevi, explained the uncommon Ottoman-French alliance of the 16th century. Shared ancestry is the genuine reasons behind François I’s call for Ottoman assistance against Charles V. Likewise, Evliya Çelebi recounted similar story. According to him, the French princess captured was in reality the mother of Prince Cem, son of Mehmed II. As is well known, Cem had lost a succession war to his brother Bayezid and taken refuge in Rhodes, from where he had been transferred to Europe and had been held prisoner by several European rulers until he had finally died while traveling along with the retinue of the French King Charles VIII. However, Evliya Çelebi took it a step further and argued that Cem did not in fact die but had instead visited his grandmother in France and faking his death and thus tricking his brother Bayezid. His descendants were still governing France at Evliya’s time. Because the two royal households were somewhat related, it was natural that the French turned to the Ottomans to help.

Bibliography

Allies with the Infidel: The Ottoman and French Alliance in the Sixteenth Century by Christine Isom-Verhaaren

Ottoman Visions of The West (15th-17th Century) MA thesis by Arda Eksigil