On X I can set the acceleration profile to 'flat' in xf86-input-libinput which provides 1:1 movement between the device and the pointer on-screen.
Section "InputClass" Identifier "My Mouse" Driver "libinput" MatchIsPointer "yes" Option "AccelProfile" "flat" EndSection
Is there an equivalent for the waylant version? Setting Options>Input>Mouse>Mouse acceleration to 1 (lowest) does not disable mouse acceleration entirely. (it's using linear pointer acceleration regardless I think)