It's been 10+ year goal to make Android BOINC (like old unofficial fork) able to use SD cards. I know since project data includes executables, it doesn't work yet, because of ridiculous new Android restrictions, but since best to run Android BOINC root (for battery life, which I do on all mine) hopefully this gets fixed soon. I know some devices allow 'adoptable storage' to combine SD card w/internal storage, so should work on most/all devices I have (at least all still used, which have instructions) or at least any I buy in future.

I want to control Android BOINC (as w/all my BOINC servers) from desktop but need RPC daemon. How would I setup?

Boinc on SD card is not recommended, as SD cards have a notoriously low error correction, slow transfer speeds, and low life cycle.
You'd be better off running Boinc off of a USB stick, than an SD card.
The ONLY SD cards I know of that have a better ECC, is Sandisk A1 and Sandisk A2 microSD cards.
They're probably the only ones that can handle at least an OS, much less a hundreds to thousands of MBs of data read and written to per day.