I still have the same issue under Fedora 41, and the same problem as other participants in this thread, namely that I only have access to Linux machines for this task. Plus, I don't want to downgrade OpenSSL to v1.1.1 due to security concerns. So although I'm not super tech savvy, I took this opportunity and put in a considerable amount of extra time to teach myself how to build the latest RockBox from source and install it manually. Can't say I regret having leant this skill, but I must admit having a working RockBox Utility would be a dream.
Does anyone know if RockBox can be installed using RB Utility from inside a Windows VM? Though the activation for my virtualised Windows 10 instance was revoked (despite the Linux host system running on the same hardware the Windows product key was shipped with) I think that may be worth a try for future updates.