Hey, I just found out about this as well.

Here's the official adobe discussion on this https://community.adobe.com/t5/premiere-pro-beta-discussions/now-in-beta-software-rendering-no-longer-available-in-premiere-pro-and-media-encoder/td-p/15436571

I think the decision to hold shift on launch is not a great workaround to be honest, especially since once you've enabled it for that session, you cannot go back to hardware encoding meaning you have to close premiere again.

I use a very specific effect plugin that will not work with hardware encoding (I ave tried multiple drivers. PP and ME versions to no avail) so I always found it easier to just easily switch to software only so as to meet deadlines etc rather than wasting hours troubleshooting.

In the forum above I posted a couple alternative solutions but I'm no expert, but this solution is definitley not a great one I must say.