What deep space objects (such as nebulae and clusters) can be seen in the northern hemisphere with ordinary telescopes? Beginners, please don't laugh if you ask an idiot. ....

Generally, beginners can see the famous M45 Pleiades cluster in Taurus and the M42 Orion nebula in Orion in the northern hemisphere with a small telescope in winter. There are many others, but for beginners, these two DSOs are relatively easy to locate, like M42, which can be seen with naked eyes when the environment is good.