A. Figure out your size in USA men's, AUS, or euro and set up alerts on second hand sites. Rm Williams goes down to a us women's 4 and will last decades.

B. Vegan leather is petrochemicals, plant based leather is still polymerization of cellulose that won't biodegrade outside of an industrial facility and both are generally faced on a poly/nylon structure. Ew. They're also both bad at being shoes.

C. No one is manufacturing recycled leather Goodyear welt boots at scale. If you want that? Buy bespoke.

If you don't care about any of the above consider anything designed by Stella McCartney. It will be vegan.