How so? One of the endings literally has geralt gift a witcher sword to Ciri. The only thing I'm confused about is how she now seems to have the witcher mutations
Have you tried running the game without the patch?
What version of wine/proton are you using? I believe newer versions of proton do what that 4GB do by default. I think it can also be forced in proton using
PROTON_FORCE_LARGE_ADDRESS_AWARE=1
but it should be on by default.