I wish I knew of another way. I emailed HomeSeer to ask just in case but according to @slagle OTA updates for ST are UTA (Up in The Air) LOL
I wouldn’t hold your breath on this because historically SmartThings has had this on their things to do and show zero progress because they have been working on bigger fish to fry namely their platform instability. In addition, when and if OTA is released to ST, it would not surprise me they only support it minimally with only products listed as compatible.
Post a new thread on your efforts to get your firmware update, I want to follow you on your progress.
UPDATE: Heard back from HomeSeer and they confirmed what you thought @kkennedy22. Here is their response:
Only HomeSeer can update the firmware on those switches. You could download a trial of our software and purchase a SmartStick+ to upgrade the firmware.