When Fantasy Flight Games took over the L5R product line, they reset the timeline. It seems likely they are specifically focused on the creation of new content instead of rehashing existing content. There are also a couple DLC that suggest perhaps that is how they will distribute that rehashed content. In the meantime, while making an entire school would require some amount of work and likely would be easiest to base it on another school; creating Clan and family bonuses should be a trivial exercise. Below I've added some potential homebrew for your convenience. Understand that these are merely suggestions loosely based off of 4th Edition.
Fox Clan
Before becoming part of the Minor Clan Alliance and later the Mantis, the Fox essentially just focused on surviving. Obviously their claim to fame is their association with Chikushudo, but that is best represented by the school and not their clan or family.
- Ring: +1 Earth (Earth is the Produce approach for Trade skills.)
- Skill: +1 Labor
- Status: 30 (Existing minor clans are 25-30, Unicorn is 30)
Kitsune Family
- Ring: +1 Earth or +1 Void
- Skill: +1 Medicine, +1 Survival
- Glory: 35
5e does not include rules for vassal families, but on the off-chance you're making a Fox-focused campaign I thought I'd include them.
Byako Family
- Ring: +1 Air or +1 Void
- Skill: +1 Survival, +1 Theology
- Glory: 30
Shudo Family
- Ring: +1 Fire or +1 Water
- Skill: +1 Fitness, +1 Medicine
- Glory: 30
I'm not going to create a school from whole cloth right now, but since "Commune with Spirits" is already a ritual that permits talking to non-elemental spirits, my suggestions for the shugenja school would be:
- A new "Summon Spirit of Chikushudo" ritual that is a starting technique for them, since I think the "Elemental Gift" effect since the ritual requires you to already be dealing with a spirit of the appropriate type.
- A school ability that allows you to communicate with Chikushudo spirits without using "Commune with Spirits" (so you can use Social skills, etc. instead of being limited to the effects)