Buildup in the pipes is unlikely. Is the toilet the only thing with drain issues? If other drains are slow too, I would think maybe a vent issue. Most mobile home vents through the roof are a small diameter, 1.5 inches or so, and can easily become plugged up with all kinds of stuff. Does the water from the tank seem to go all at once like it is supposed too, or just trickle out slowly? Did the slow flush happen all at once? It is also possible there is something wedged in the trap of the stool. A stool auger is an easy way to clear it out.

Is it swirling but not flushing? If so, it could be that water is not entering the bowl quickly enough. Take a bucket of water and dump it into the bowl. Does it flush? If so, you may just need to clean out the holes under the rim to allow water in more quickly. A drill bit works well.

The other drains have no problems at all. It's just the toilet. I'll try cleaning out under the rim. Then I'll try something through the trap. Do you think one of those cheap hand held snakes would be sufficient?
Thanks.

A drill to unclog the holes? Bad idea, you'll crack the bowl. Even wire can be dicey.

Best thing I've found is a cable tie or zip tie - the thin end. Very flexible, yet stiff. You could put CLR in the tank and let it sit overnight, see if that helps too.

Snaking wouldn't hurt, but are other drains slow too?

What happens if you flush it empty, still slow? You could also have a collapsed pipe or tree roots, in case you need Roto Rooter or similar, and possibly new pipe or a sleeving system.