Craft Personal 3.0.0-RC2 doesn't show the Pro Trial offer anymore? Is that correct? I did install a Pro License however this triggers the system to change the domain (from local dev to live) which is unwanted.
Nothing around trial usage has changed between Craft 2 and Craft 3, so as long as you follow this, it should work:
Just keep in mind (because it sounds like you're swapping license keys around) that license.key info is cached for 24 hours at a time, so be sure and clear
craft/storage/runtime/cache in whenever you do something like that to get accurate results and hit the updates page if you need to force a call home to Craft's web services.