Is it permissible for someone afflicted by "possession" (mass) to attend religious lessons and lectures, given the possibility of actions that could harm attendees, or is it better to refrain and suffice with self-learning?

Dealing with illness with the conviction that it is a "touch" (of jinn) is not wise, as such touch is rare, and most disturbances result from psychological or organic causes. All means of treatment must be pursued by consulting mental health specialists, while maintaining remembrance of Allah (dhikr) and reciting the Quran as a means of protection and healing.

As for attending circles of knowledge, if the disturbance is minor and tolerable, then there is no harm. However, if it is frequent and disruptive, it is not advisable; because the Prophet ﷺ forbade harming others by raising one's voice, and this applies even more so to one who raises their voice due to their illness. Jurists have stipulated preventing those who cause disturbance from entering the mosque, to uphold the sanctity of mosques and circles of knowledge. However, if the disturbances are rare, there is no harm in attending, and it is preferable to have a companion who can help manage any disruption.