Although compiling the kernel took an hour, all I had to do was add this 
to drivers/input/mouse/elan_i2c_core.c

{ "ELAN061D", 0 },

This went along with a list of other ACPI IDs, so the number may vary with 
different models. I hope this gets fixed upstream so others won’t have 
to wait a long time compiling a kernel to get it to work. 

The above links can fix you Lenovo 300 series (amd) touchpad (i2c) linux problems, however if you noticed error messages such as

cp: cannot stat '../i2c-amd-mp2': No such file or directory
Error! Could not find module source directory.
Directory: /usr/src/i2c-amd-mp2-1.0.0 does not exist.
Error! Could not find module source directory.
Directory: /usr/src/i2c-amd-mp2-1.0.0 does not exist.
Error! Could not find module source directory.
Directory: /usr/src/i2c-amd-mp2-1.0.0 does not exist.

or

"File: /usr/src/i2c-amd-mp2-1.0.0/dkms.conf does not exist." ....

as of march 2019 the install script copy portion of the script is buggy. simply manually copy the contents of the zip directory. open a terminal and cd to the directory where the files are uncompressed, then copy all:

cp * /usr/src/i2c-amd-mp2-1.0.0/

now run the install script as a superuser. With the bit of manual help, the script should complete and end you lenovo headache:

./dkms-install.sh 
About to run dkms install steps...

Creating symlink /var/lib/dkms/i2c-amd-mp2/1.0.0/source ->
                 /usr/src/i2c-amd-mp2-1.0.0

DKMS: add completed.

Kernel preparation unnecessary for this kernel.  Skipping...

Building module:
cleaning build area...
make -j4 KERNELRELEASE=5.0.4 -C /lib/modules/5.0.4/build M=/var/lib/dkms/i2c-amd-mp2/1.0.0/build....
cleaning build area...

DKMS: build completed.

i2c-amd-mp2:
Running module version sanity check.
 - Original module
   - No original module exists within this kernel
 - Installation
   - Installing to /lib/modules/5.0.4/kernel/drivers/i2c/busses/

depmod.......

Backing up initrd.img-5.0.4 to /boot/initrd.img-5.0.4.old-dkms
Making new initrd.img-5.0.4
(If next boot fails, revert to initrd.img-5.0.4.old-dkms image)
update-initramfs.........

DKMS: install completed.
Finished running dkms install steps.