Your best best for a portable/everyday solution is the Nikon p900 super zoom type cameras, they are cheap and compact enough and have enough zoom for reasonable ID purposes, the IQ is 'bad' though for artistic/high quality photos. Artistic setups for long range photography weigh a lot, cost a lot and are bulky as hell, sports/wildlife photography setups basically.
Yes it is very hard to keep small distant objects in frame and more importantly achieve focus, it takes practice, just take it out on a clear day and practice with planes. Keeping the mass central is key, find something to rest it on or lean on (wall/tree/car/building etc.)
So many UFOs even shot with high zoom cameras are just camera artefact's from the object (plane/star) not being in focus, it can very hard to get focus on a small object in the frame.
When shooting something that does not fill anywhere near the frame auto settings will let you down, auto exposure will try to average the scene but your UFO might not even register for it as it is small, even zoomed in a plane fills only a small amount of the screen, learn about this and understand, for ID purpose shutter speed is key keep it high at the expense of everything else (shutter priority)
Also a lot of the time you might be shooting "lights in the dark" where even zooming in on a light doesn't actually show anything because it's a point light source. There might be an object there say a plane but there's no way the camera will expose for it automatically and if you try to manually expose there's not enough light to show the body of the plane and the light will over expose and glare in the image. There are just some scenarios where the camera is not going to show what is there, understanding the limits are is key. This is is big with people shooting planets/stars because there is nothing but the point light source there, the artefacts become the UFO (donut shapes/morphing UFOs etc.)
Having the tool and then misinterpreting what it shows is common in UFO videos, camera shake, over/under exposure, bokeh and the various types of lens aberrations and lens flare/glare/motion blurring are all common sources of UFOs even taken on a zoom camera.
The other things to keep in mind are to shoot in RAW if you can (recording the RAW sensor data is the most information and the best for analysis) make sure your clock is right on your camera, or set to UTC. Make sure you understand the metadata. If your camera does not have GPS receiver record a GPS track of where you are on your phone so your photos can be sync'd to the GPS track later on and views compared with google maps etc. Take wide angle shots as well as zoomed in shots. Video what you can but also take stills as they will be higher quality.