Interestingly, quantum mechanics is already sort-of fully deterministic. It's only the not-quite quantum mechanical Born rule that's interpreted as probabilistic (unless you believe in eg the many worlds interpretation.)
Admittedly it's been a long time since I've studied quantum mechanics! Has the thinking changed?
The Many Worlds interpretation doesn't have the collapse, it says that all the possibilities happen.
https://en.wikipedia.org/wiki/Many-worlds_interpretation
> In contrast to some other interpretations, such as the Copenhagen interpretation, the evolution of reality as a whole in MWI is rigidly deterministic.
There's some wrinkles in that interpretation to preserve the Born rule of observed frequencies.