I’m with AussieBroadband now for fixed (was Optus cable). Still on Optus for mobile. AussieBroadband have IPv6 in beta, but works fine for me. See https://forums.whirlpool.net.au/thread/9004zpv9
What do you get?
A direct /128 out of a /64 range for your wan side of the connection.
A /56 which can be used for LAN side connections. This can be split up into /64 ranges via PD (Prefix Delegation), or manually configured by you.
I’m sure there are more providers with IPv6 too. I know Superloop also started beta recently. See https://forums.whirlpool.net.au/thread/97rn1z23
Internode were the first Aussie ISP with IPv6. Looks like they still provide it too. https://www.internode.on.net/support/guides/internet_access/ipv6/ Not sure what subnetting they use
I also went with AussieBroadband. You do need to 'opt in' after being connected - Took all of 10 seconds to do from their support page.
Other providers include Foxtel's NBN ISP offering is dual-stack IPv6, and Exetel also has IPv6.
https://stats.labs.apnic.net/ipv6/AU shows the latest measurements of IPv6 deployment, look for the entries >30%.
AussieBB is actually low in this report, possibly reported under a different ASN - as I can confirm its working well.
Aussie allocated a /56 for the LAN, different from the /64 used for the WAN subnet.