Hi Jason and @Nicholas_Bokulich,
There is a post about using GG2 with SEPP here in conjunction with @wasade.
"Given these observations, it now seems viable to use SEPP with Greengenes2 to obtain a phylogeny from arbitrary amplicon sequence variants. A Greengenes2 2022.10 reference compatible with q2-fragment-insertion can be obtained from the Greengenes2 FTP."
-Celeste