Overall, it's pretty close. The show captures the essence of the comic, but there are some changes in details and pacing to make it work better on screen. Some fans might notice these, but they don't ruin the experience.
It's reasonably faithful. The main plotlines and character developments are similar, but there are some minor differences for the sake of the TV format.
The Umbrella Academy series mostly sticks to the comic. However, there are a few additions and alterations to make it more engaging for a TV audience. But the core elements and the charm of the comic are intact.