First usage question: Removing UDEV/EUDEV?

Since this is a drop-in replacement for libudev/libeudev, should I purge libudev/libeudev before installing this on the system?

The problem is that Devuan seems to heavily depend on libeudev, and purging it will purge fudamental parts of the system too:

The following packages will be REMOVED:
  apt* apt-transport-https* apt-utils* d-shlibs* dmsetup* eudev* fuse* i2c-tools* init* initramfs-tools* initramfs-tools-core*
  libapt-pkg6.0* libdevmapper1.02.1* libeudev-dev* libeudev1* libfido2-1* libparted2* libpci3* libusb-1.0-0* mount* ntfs-3g*
  openssh-client* openssh-server* openssh-sftp-server* parted* pciutils* rpi-eeprom* rpi-eeprom-images* sysvinit-core* usbutils*
  util-linux*

So, any notes on how to proceed in this case?

I guess you can build libudev-zero as deb package providing libeudev. This is how i made it work in Artix

@phkrl: That's a GREAT idea! Hadn't though about that possibility... I will take a look.

Do you have instructions for that? ie: building a package that provides another package...

Do you have instructions for that? ie: building a package that provides another package...

It entirely depends on package building mechanism. I never built deb packages, for Artix (which uses Arch format) supplying provides=(...) in PKGBUILD is enough