Is the regular gathering in the mosque on Friday after Maghrib prayer to memorize the Quran, learn its recitation, or recite parts of it considered an innovation (bid‘ah), by virtue of its repetition and resemblance to repeated obligatory acts?

Setting a regular time for seeking knowledge is not an innovation (bid'ah), for the intent is the knowledge itself, not worship at a specific time. Imam Al-Bukhari titled a chapter: "Chapter: One who set known days for the people of knowledge," and he cited the hadith (definition) of Ibn Mas'ud, who used to remind the people every Thursday, out of fear of boring them. This is also what the Prophet (peace and blessings be upon him) used to do. It can be inferred from the hadith that it is desirable to avoid excessive continuous performance of good deeds, out of fear of boredom, while observing one's energy levels.