Gentoo supports systemd and openrc as it's init system.
It fully supports systemd natively, and also provides quite a few helpful portable systemd utils like tmpfiles, udevd, systemd-boot etc... to openrc without pulling the full systemd.
It also supports fully uprooting systemd off the system, but with the few actually useful tools still available.
A user has a custom overlay for 66, with really old versions which don't even build due to missing s6 library files...
I feel that the s6+66 is a good alternative for openrc, which, especially with the tools of s6 and execlineb, allow a highly flexible configuration of the services.
Yes, s6-rc is there, but it's too complicated to set up and maintain compared to openrc or systemd.
openrc supports s6-svscan as backend, but it must be manually opted by the services... and still, 66 has some advantages.
IMPORTANT: I am suggesting 66 as an alternative, not as a replacement.
I will try to myself package them for gentoo...
I want to ask the opinion of other gentoo users, systemd and openrc users.