Black smoke rings can have a variety of causes. To name a few, they can be caused by the explosion of an electrical transformer, a home-made trash can smoke ring launcher, fireworks tests, or other pyrotechnics. They generally do not occur naturally and are nearly always the result of something man-made.
There are many potential explanations for sightings. We recommend eliminating the most common and mundane before jumping to less probable conclusions or you submit a report.
Live flight tracking maps are available for monitoring airline traffic and trajectories in real-time or historically around the world.
Planned launches occur regularly all over the globe. These tracks can help identify the potential missions or launches in your area.
Satellite tracking can also be done in real-time with the aid of tracking maps. They are also helpful for tracking Starlink launches.
There are a number of sites which track solar flares, magnetic storms, and other events which are helpful for eliminating explanations related to astronomic phenomena.
French site (with English translations) with resources and examples covering the most commonly observed phenomena and explanations for UFOs.