Figuring out available memory on nRF52

I’m not sure where to post this, apologies if this isn’t the right place.
I’m using this PR Add Xiao nRF52840 (Sense) board support by maxgerhardt · Pull Request #151 · platformio/platform-nordicnrf52 · GitHub to program a Seeed Xiao nRF52 and am wondering how much free memory I can actually use for my program.
I’m using the Arduino framework and it’s not clear to me which dynamic allocations are done outside of my program, either by the Arduino layer, or the FreeRTOS one (and I’m not sure how much is done with it).
Assuming I’m not using any library, and I statically allocate everything I need, do I have to leave some free memory for hidden heap allocations by platform libs ?