I don’t know about the method you used but this can be configured in the config.js file, look under the Video Section :
Video
// Sets the preferred resolution (height) for local video. Defaults to 720.
// resolution: 720,
// w3c spec-compliant video constraints to use for video capture. Currently
// used by browsers that return true from lib-jitsi-meet's
// util#browser#usesNewGumFlow. The constraints are independent from
// this config's resolution value. Defaults to requesting an ideal
// resolution of 720p.
// constraints: {
// video: {
// height: {
// ideal: 720,
// max: 720,
// min: 240
// }
// }
// },