Should the toilet drain pipe gasket be installed?

How can I best reinstall the gasket on the toilet waste pipe in the wall.

The pipe has a small collar at the front where the gasket is slid back on, but I can't get it under anymore. I have already warmed up the pipe with a heat gun, but it just doesn't work.

Maybe you have another tip for me

Here are a few more pictures of an old bow where the sealing is still inside.

Hi Swabian

The shown bend has a factory-installed and normally non-removable lip seal.
The new seal does not fit in there.
You have to replace the entire bend.

Olli