A tiny mod to make dismounting separate keybind (R by default, can be changed back to shift). This is a client mod but can be installed on a server (and if you do that, it will be required clientside). I'm not responsible for this mod potentially triggering some anticheats (I have never tested it on servers with anticheats, but it does something that is not possible in vanilla)
This also has the side effect of allowing to sneak while in a boat or minecart.
This coremod doesn't fully follow forge guidelines because it's so small that signing it is more work than it's worth.