I just tried this with JPGs from a USB thumb drive. Works pretty good, free, and is already on your computer (maybe?).
*open File Explorer and Movie Maker
*select JPGs from USB thumb drive and drag them to Movie Maker
*can set each JPGs time length with EDIT in Movie Maker upper taskbar (1 to 30 seconds), if need longer times could save as lion1.jpg, lion2.jpg, etc. for same JPG. If you don't use a transition between these 'identical' JPGs, JPGs will appear to be 1 JPG for whatever length you choose. JPGs can have different time lengths.
*could use ANIMATION for JPG transitions
*could add MUSIC or NARRATION to slideshow
*when finished click FILE, SAVE MOVIE, then I select FACEBOOK. Type in a name for your movie and click SAVE.
*After opening saved movie file, could click on 3 dots (options menu) in lower right corner and click REPEAT if you want the file to play continuously. If you use REPEAT and Transitions between JPGs, you might add a Transition to your first JPG. Can also select Full Screen, mini view, play, pause, cast to device, etc.
Slideshow (movie) plays on my W10 desktop and works for Twitter also. While I haven't used this method for a JPG slideshow before today, I've used it for tweeting 'game camera videos with sound'. Twitter has a video time limit for attached video files, maybe 45 seconds. Movie saves as *.mp4 file.
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I tried PHOTOS, but couldn't find a way to change the display time for each photo (about 4 seconds); and if you save a JPG with different names, the slideshow will not show them as one 30-second photo.