I mostly followed [these instructions] for how to set up dual-booting on my macbook, and everything seemed fine, up to the very last step. Now when I reboot the system (even if I hold command-R) I don't get any rEFInd boot menu or recovery mode, it just boots to the Ubuntu partition and I have no way of booting into OSX, which means this is now just a single-boot option Ubuntu machine. I suspect it may be because during the OSX partitioning, I created two partitions, and then consolidated them into one during the Ubuntu installation phase.
What should I do from this point?
Edit solved: From within Ubuntu, install refind again from the secondary installation. In case of Ubuntu:
sudo apt install refind
Let the program install to the partition that it wants to install to, then reboot, and you should see the rEFInd menu again.