EDIT: in my 1st answer, I overlooked PC-less operation, so some correction here. But I still think, that firmware upgrades are useful and should be performed. You can at any time look into the readme file of the fut_tool's ZIP archive, what has been fixed to decide, whether an upgrade would be worth.
Even if EKBluesboy states, that he has no PC in his listening chain, some updates, and fixes by firmware might also be important for him for the general operation of the device. See below the list of changes between v48 and v55.
An interesting new use case might be to connect the device temporarily to a PC to make some useful PEQ adjustments for his listening chain, by using the new ADI-2 Remote software. It offers a much easier way to configure / operate the device and to make PEQ adjustments, but it requires at least firmware version 54. Here are the links to the prerelease for Windows and Mac:
Mac: https://forum.rme-audio.de/viewtopic.php?id=37669
Windows: https://forum.rme-audio.de/viewtopic.php?id=37784
For some types of devices I would be careful, right, also e.g. in terms of BIOS upgrades for a PC. In the case of RME devices, it is a different story. RME Firmware updates are well tested and bring important bugfixes and often interesting useful features like in this case.
These are the differences between Firmware version 48 and version 55, I extracted them for you:
07/17/2023: ADI-2 DAC 80/55: PEQ On/Off no longer causes a change to Preset Temp.
07/11/2023: ADI-2 DAC 80/54: adds MIDI port and support for the ADI-2 Remote. <----- !!!!!!
ADI-2 DAC 78/51, ADI-2 Pro 263/116. Pro/DAC Fix: Corrected display of B/T setting >9.5 dB in Dark Volume Screen. Bugfix Pro: 1 sample channel offset when SRC is active with an ADAT input signal.
05/19/2022: ADI-2 DAC 78/50, ADI-2 Pro 262/115. Bugfix: A preset name consisting only of spaces caused the device to freeze. AutoRef DSD did not work correctly on devices with AK4490.
04/11/2022: ADI-2 DAC 78/49, ADI-2 Pro 262/113. The option Do not load Volume did not always work as expected. Loading the Factory setup now also follows that option. B/T can now be used in both PEQ and as B/T at up to +/-12 dB. Remote Locked now allows to use the volume keys on the remote. Pro only: In Dual EQ mode a graphics refresh was missing in the Bode plot. In Dual Phones mode with AutoRef active, inserting a TRS jack into Phones 1/2 could cause a wrong dBr setting.
The update process is explained in the manual, here are the gory details in short. A firmware update is not difficult, but it requires an installed driver under Windows and Apple and you need to connect the device to your computer via USB. If you start the fut_tool, it will display to you the installed firmware version and whether an update is needed.
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14