systemd is not required, it’s just the default that the installer has support for.
You can still use the old-style suspend & resume by not setting the NVreg_PreserveVideoMemoryAllocations=1 module parameter for the nvidia module. From your bug report it looks like you don’t have that set, so nothing is supposed to have changed about suspend & resume.
If you do want to try the new suspend path, the only requirements are to set NVreg_PreserveVideoMemoryAllocations=1 and then be sure to trigger nvidia-sleep.sh before suspending and after resuming. That’s what the systemd units do but you can do it yourself using a script or something.
#!/bin/bash
/usr/bin/nvidia-sleep.sh suspend
pm-suspend
/usr/bin/nvidia-sleep.sh resume(replace pm-suspend with whatever your actual suspend command is).