The stock rear rim on my bike got bent pretty badly and a bicycle shop replaced it with a new one. I hate the new rear rim! Its almost impossible to get off-on any tire! The front rim is the stock and removing-installing tires is super easy. I can't take it anymore! Im seeking for a new rear rim replacement. How do i choose one that is easy to deal with?. My bike is 26 inches
I have selected two cutaway section drawings of different rims from the same manufacturer for this example. They are a similar sort of width and profile but have significant differences.
Regarding tyre fitting, to seat or unseat a tyre, the bead has to be able to go into the rim's well in order to pass over the rim wall, otherwise it would be impossible (the tyre bead is a smaller circumference and doesn't stretch).
The Chukker is a more classic design with a deep, even bed/well that the tyre bead can sink down into more easily when deflated. Tyre removal and fitting is fairly quick and painless.
The Aileron has a more modern rim bed design featuring a deeper central well and two shallow shoulders that the tyre bead will pop on to when inflated (this is also how tubeless tyres achieve the air seal though not all rims with this bed profile are tubeless compatible). To fit or remove the tyre from this rim, the tyre beads have to be moved into the central well or the tyre is impossible(difficult) to remove or fit. Sometimes it's necessary to go around the tyre a few times to keep working the beads back into the centre to allow the operation to be completed easily.
If you spend a little time looking at the rim profiles here and the two on your bike, I suspect that you will have something similar (one of each). The manufacturer of the rim and the outside appearance isn't relevant in this case. And nor is the number of spokes in the wheel.
Some rim/tyre combinations are tighter than others. The difference in circumference can go from tight to easy within millimetres.
Your new rim seems to be slightly larger than the original, while still being 559mm in total diameter.
One solution is to check the valley in the rim, and when fitting/removing tyre make sure that the bead sits down in the valley. That change in technique might make all the difference. And it doesn't cost you anything.
You might also consider a slacker tyre - Marathon are known to be tight, there must be some that are looser.
I do not recommend to shave anything off your tyre's bead - that way leads to weak spots which could fail, and rough/high spots that could abrade your tube and flat.
Also, "bending" the rim is not going to gain you anything useful. All that would do is put the rim out of true, and give you a non-flat braking surface if its a rim brake.
Upshot technique. There's a deeper write up of the method at https://bicycles.stackexchange.com/a/63961/19705
I recommend selecting a rim that is not intended for tubeless tires.
I bought some time ago a bike that had tubeless ready wheels. Changing the initially installed tube-type tires to some more reasonable tube-type ones was a major chore. I even punctured one inner tube in the process and spent probably way more than an hour for both wheels.
The tubeless ready wheels unfortunately had less than 36 spokes, so it's easy to deduce that the disc brake front wheel lost tension on all spokes and the rear wheel lost tension on some spokes. The "solution" of the bike shop where I bought the bike from was to put thread glue into all nipples, and tighten all spokes into low and non-even spoke tensions. Now the rear wheel creaks when climbing up a hill seated.
Because these preinstalled wheels were not good enough, I built a new wheelset from 36 spokes each wheel, a non-tubeless-ready rim with double eyelets and Shimano cup and cone bearing hubs. Installing a tire is easy: I don't even need tire levers on these rims.
I suspect you'll find the same, that a tubeless ready rim is hard to install a tire on whereas a non-tubeless-ready rim is easy to install a tire on.