Here I go again, the mad clog guy! Walkley Clogs (W. Yorkshire, UK) hand make BIFL footwear with a wooden sole, mine are new (veg tanned) leather as I made the judgement call that it was preferable to buy something leather that would last 20 years, than petrochemical based which might last 5. After 3 and a half years of daily use still look basically new. If you want to further reduce plastics you could also opt for clog irons, but these are -5 grip, -20 stealth!

They do now do vegan leather (I've not seen / touched / handled it so won't comment on the quality or suitability) - although their website doesn't list it as an option for boots they might if you drop them an email or facebook message, and they also resole ex-army boots (UK size 6 and up) onto a clog sole, and have in the past resoled customer provided boots too.

Vegan leathers I've seen don't wear as well as real leathers yet, from the docs I've seen they are really susceptible to pinch failures where the sole bends (new leather docs also suffer this) - obviously the advantage a clog sole has is that there is no flex at all which removes this failure mode entirely.