I confirm this. Same situation even with videos with landscape ratio video files shared by public link. Control buttons and part of the videos are not visible without scrolling down. Nextcloud 27.0.1, checked with Chrome and Firefox 115.

Also confirmed.
Still happening in Nextcloud 28.0.1, also with videos in landscape ratio and shared by public link.

Same here on 28...

Also on NC 29.

In 27.1.11:

If I do:

.view__file {
  margin: 0 auto; 
}

#imgViewer .view__file {
  height: 100%;
  width 45vh;
}

It seems to remedy the issue. Obviously I need to do some more testing but if it looks ok and the NC devs haven't already fixed it I'll create a pull request.

I think I tracked it down to the Videos.vue file. It has the max-height attribute set to 100%. If I remove that, the video displays correctly across desktop and mobile.

Could someone open a PR with a fix? :)

Could someone open a PR with a fix? :)

Done:
#2349

For those who don't want to wait the PR to be merged, you can fix the bug with the Custom CSS application and by putting this CSS:

#preview video {
  max-height: calc(100vh - var(--header-height) - 65px - 200px - 16px) !important;
}