FPGA 198 Antero is up in the download section of this site. It’s in the “PerfectWave DirectStream DAC MK2 v2.3.6” package.
The “How to Upgrade DSD MK2 firmware.txt” file contains the update instructions in section 2. (The instructions say the version screen should say “178-Beta SS”, but instead it should say “198-Antero”.)
I just want to add that I’m not done with stomping pops, and if I (or you) find any, I’ll try to get those in the April release.
[Edit: - A few updates: Use FAT32 on your USB stick. And you may need to turn off the Mk II before you put the USB in, and then turn it back on to get it to read the list of FPGA releases off of the USB stick.]