When changing a traditional formatted comic over to webtoons/mobile format, there's a couple things that need to be taken into consideration. Wide frames might have to be chopped down into smaller frames. I prefer to try to space them out to continue that sense of time progressing.

Smaller screens mean that text can be harder to read after it's been scaled down, and scaled up bubbles might not fit comfortably within the frames. My first approach is to remove the bubbles, fill in the background image with lineart and colours to match the original version, and organize the bubbles in a way that doesn't disrupt the flow of the story if possible.

Variation of frame size is also helpful to preserve that feel of a comic without sacrificing too much of the readability. If need be, I like to stack them left to right, especially if the events being told are closer together in time, so the reader gets a sense of things progressing more quickly.

Combining these approaches, I've found the conversion process to be approachable and straightforward.