I can also confirm that CHDK loads on ELPH300HS 1.01a; things like file browser, games, "make card bootable..." work, but saving in RAW and AV exposure bracketing do not, and I can load and run the "Ultra Intervalometer" script, bit it only takes the first shot.
Overall thanks for the great work!
What needs to be changed in capt_seq.c and movie_rec.c files to make it work? I only have a bit of C++ experience, but maybe there's something I can help with?