I'm in the same situation -- haven't done a 706 for several years, now have two I would like to finish before tax season.  A couple thoughts:

1) There is a company that sells the 2024 software for $170.  Assuming your client estate is worth several million, is that too much to ask them to pay for your convenience?  Add in more, of course, for installing and learning the program's quirks.

2)  Are the schedules and forms any different from 2023 to 2024?  Is the only change, the first couple pages where the computations are done?  Can you use the software for everything but those, and then do those manually?  It has to be a paper, mailed-in return anyway.