>>393126379
There are some FBT options that works without index, but those are relatively new and likely not available soon.
https://en.shiftall.net/products/haritorax
Another option is just get base stations and the trackers and do a hybrid setup, but I've had issue getting my base stations to register without connecting an Index headset first. From what I understand, you need a base-station capable headset to initialize the base stations in the beginning. I think people that run hybrid setup have both index and quest and use the hybrid for the wireless feature.
tl;dr: just get an index