Can't update r610 iDRAC

Is there some sort of a bootable ISO sure-fire way to update a very old r610 iDRAC that can't be updated via GUI? The r610 is running VMware ESXi, so installing Windows on it for the sole purpose of updating the firmware doesn't seem to be a good option. The SUU ISOs (like DELL EMC Server Update Utility, Windows 32 bit Format, v.17.12.00) are 2x-sided at around 9GB and I don't have 2x-sided DVD blanks at the moment.

Seems to be a recurring theme:

• r610 with a really old version of iDRAC. Initially couldn't connect to its web GUI:
  "This site can’t provide a secure connection
  uses an unsupported protocol.
  ERR_SSL_VERSION_OR_CIPHER_MISMATCH"
• Then through IE compatibility mode and enabling TLS 1.0, was able to get to the login page - yet after entering correct credentials, the GUI would just go back to the login prompt and eventually display "session limit reached".
• I can login to it via SSH but it seems of little use: "This Integrated Dell Remote Access Controller does not support RACADM commands. Please contact Dell Customer Service to upgrade your version of iDRAC." Same error when run racadm remotely from a different host with "-r -i" options.
• The iDRAC is "Express" (not Enterprise) version - which is why I am assuming racadm isn't an option?
• Tried "Systems Build and Update Utility" from 2013 - can't boot to it from a DVD but then when I try to start "firmware upgrade", it says, "can't find SUU".

So in other words, can't seem to be able to update iDRAC firmware because:

• Can't log in to Web GUI even if I get past the SSL error: the GUI resets to login prompt.
  • (Even if I reset iDRAC to defaults, and then log into its GUI, iDRAC update hangs on "uploading..." and then again, resets to login prompt. I did try firmimg.d6 and not the full package.)
• No local or remote racadm option: "This Integrated Dell Remote Access Controller does not support RACADM commands."
• OME can't access it, yet even if it could, it doesn't appear to be supported: our other r610 servers do not show any firmware updates or other patches available in OME.
• "Dell Repository Manager (DRM)" no longer supports r610, it seems.
• The server runs VMware ESXi OS, i.e. can't try to run firmware updates from Windows.

Ideas?

Thanks!