I read about there being methods applied by ISP's to defend networks against IPv4 spoofing, but not too much about IPv6 spoofing. I'm wondering if someone has some knowledge if ISP's apply techniques against IPv6 spoofing.
Actually, there's not that much of a difference. The same techniques available for IPv4 can be applied for IPv6. Reverse path filtering (RPF) and static access-lists are the most common used, but given a specific network and its design other techniques can be used. MANRS has a nice overview on anti spoofing techniques for both IPv4 and IPv6: https://www.manrs.org/isps/guide/antispoofing/