Hello seblec,   I do see that iDRAC8 2.75.75.75 has not made it to the catalog yet, as you have seen. I am sorry about that.   You can use the same update you used for the R730XD for the R730's.   Version 2.75.75.75 is posted as a Recommended update. Only Urgent updates get added to the catalog outside quarterly updates.I would suspect it will make the next update in a couple months.    I hope this helps. 
Hi! I did have to upgrade a PowerEdge R730xd from v. 2.70.70.70 to v. 2.75.75.75. And it's fine. But we have a lot of PowerEdge R730 that couldn't be seen in OME (OpenManage Enterprise) as to be upgraded to v. 2.75.75.75. The catalog from Dell is up-to-date. I tried to add a second one via HTTS manually. Same results. As I could read it here, they should be available and eligible to v. 2.75.75.75 upgrade. Even weirder, the PowerEdge R730xd is seen as retrogradable to v. 2.70.70.70. Why? I can't get it… is it the catalog corrupted about this version? Or not updated yet ( there are no references to 2.75.75.75 in catalog file). But the release if from June 2020! Thanks!
Why OME still doesn't know about iDRAC v. 2.75.75.75 update?