Praise be to Allah, and may peace and blessings be upon the Messenger of Allah. To proceed:
First, matters of the unseen should be limited to what has been established in the Qur’an and Sunnah. We should not become preoccupied with details for which there is no authentic evidence, because knowledge of the Dajjal’s circumstances before his emergence cannot be based on speculation or stories, but only on what has been authentically reported from the Prophet ﷺ.
There has been scholarly disagreement regarding some individuals who displayed characteristics associated with the Dajjal. The most famous of them is Ibn Sayyad, but the hadiths do not conclusively establish that he was the Messiah Dajjal who will emerge at the end of time.
As for the authentic hadith concerning the story of Tamim Ad-Dari, may Allah be pleased with him, he reported seeing a great man shackled in iron on an island. The man stated that he was the Messiah Dajjal, that he was waiting for permission to emerge, and that when he emerges, he will travel throughout the earth but will not enter Makkah or Madinah, because the angels will prevent him from entering them.
The Prophet ﷺ affirmed Tamim’s report and explained that what he had related was consistent with what the people had already been told about the Dajjal. Therefore, this hadith is an important basis for understanding his condition before his emergence.
Accordingly, there is no authentic evidence establishing that the Dajjal is currently roaming among people, taking different forms, or entering Makkah and Madinah while in disguise. Rather, the apparent meaning of Tamim’s hadith is that he is restrained and shackled and will remain so until he is given permission to emerge.
It is better for a Muslim to focus on what benefits him in preparing for trials, increasing acts of obedience, and seeking Allah’s protection from the trial of the Messiah Dajjal, rather than becoming preoccupied with unseen details for which there is no established textual evidence.
And Allah تعالى knows best.