How (un)popular is Donald Trump? FiveThirtyEight has maybe the most fine-grained answer with its real-time tracker which mixes data from various pollsters.
You can explore the evolution of Trump’s approval ratings and compare him to his predecessors across different timespans (during the first days of their presidency, or during their whole mandate).
But what’s key here is the granularity and transparency of the analysis. Unlike most political reporting about Trump’s popularity, here you can easily assess the credibility of the source by yourself thanks to a handy pollster rating system (each one is ranked from A to F). You can also filter data depending on responder status (to exclude unregistered adults for example).
It’s a good resource for the political nerd, or just for any citizen actually.