Toilet water drains out slowly after flush
I have had this happen on toilet models that have a vertical tube and not a flapper.  These are called no-flapper style.  Here is a link to a particular model: https://www.plumbingsupply.com/mansfieldtoiletparts-claro.html

The vertical tube looks sort of like an upside down trumpet, where it forms a seal at the base of the tank.  Two things can happen with these.  One is leaking at the bottom due to calcium buildup, that can be cleaned with vinegar and a toothbrush.  There is also a gasket that might need to be replaced.  The other is that the flush valve gets stuck on the part of the tube where the flush valve inserts.  Cleaning off the flush valve arm to make sure it is smooth and slippery, and doing the same to the part where the flush valve arm inserts, has helped.  But ultimately, what I ended up doing with these in the long run was to take the toilet apart and replace them with the flapper style.