Ham1255 I dont have another android phone to test it out. But i have seen posts on other platforms suggests that since android 7 it was supported, so i had no option but to ask here.
Reading around a bit, I think this is complicated.
For example, this StackExchange post points to code which appears to support IPv6 tethering (including, I think hotspot) in Android. But the code contains a bunch of conditions that must be true, so it seems possible that in some situations a phone would have an IP address but not be able to activate an IPv6 hotspot.
Also, it seems this issue may depend in part on a long-running battle about how to do endpoint configuration in IPv6. Here is a post on this forum which leads to this extremely long thread on Google's issue tracker.
Overall, it seems possible that current Android (including GrapheneOS) might support IPv6 hotspots on some IPv6 networks but not others.