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Start your Tor with

ORPort 9001
ORPort [2a01:238:43e4:2b00:ae5a:a980:1f63:cc5e]:auto nolisten
DirPort 9030

and let it start up. Then go to http://127.0.0.1:9030/tor/server/authority and check out how it has the line

or-address [2a01:238:43e4:2b00:ae5a:a980:1f63:cc5e]:94

First: How did it pick that number? It's a weird choice for a port.

Second: If this is actually your ipv6 address, you can leave out the nolisten, and that's where things get interesting. Your logs will say something like

Nov 24 01:53:42 v4 tor[10988]: Nov 24 01:53:42.001 [notice] Opening OR listener on [2a01:238:43e4:2b00:ae5a:a980:1f63:cc5e]:0
Nov 24 01:53:42 v4 tor[10988]: Nov 24 01:53:42.002 [notice] Opened OR listener on [2a01:238:43e4:2b00:ae5a:a980:1f63:cc5e]:41535

but then your descriptor will still say :94.

This is happening right now to relay "Testbit": they have set :auto for their ipv6 address in their ORPort, they get the above line about how it's opened on port 41535, and yet their descriptor says it's on port 94.