From some of them comments it seems like there is an option to upload a firmware to it, they just haven't released any updates yet. Is that not the case for you?
Regardless, I wouldn't expect to see too many firmware updates for these switches anyway unless major functionality is broken.
Based on the hidden menus I found on my managed Hasivo switch (using a different management UI), these manufacturers might not even need their own developers. There were UI menus to upload a new logo and to change the company name, copyright year, default configuration, etc. In other words, they seemingly don't even need to recompile the firmware to change those. Still, there were some other assets inside the firmware image that weren't used and couldn't be uploaded that way, so they appear to at least be repackaging the firmware image contents at the very least.