@WALDIR21, there are three general methods to convert vertical to horizontal, and all were brilliantly illustrated by @Hudson555x in a previous post to you:
Of those options, #2 and #3 can be configured to cause zero loss of quality. Technically, #2 would require a custom video mode that had 1920 height in that particular example. However, a video that’s 1920 tall would get shrunk to 1080 for playback on a FullHD screen anyway. So, for practical purposes, option #2 still counts as zero loss of quality even though the vertical resolution gets shrunk to 1080 with default FHD settings.
Option #1, the “crop and zoom”, might be called a loss of quality, but that’s only because the source video didn’t have enough pixels to fill the screen in the first place. This is a problem with the source camera, not a problem with Shotcut or post-production processes. A higher-resolution video from a better camera would have extra pixels that would enable zooming in without interpolation being needed.