I recently stumbled upon a problem with default MacOS bootloader. The scenario is next: My Macbook pro 2012 only has one 256 GB drive from where I specified 70 GB's of space to be used as Ext4 partition that'd run Linux Mint. When I installed mentioned Linux distro, I ran the following command in terminal, that was supposed to install rEFInd and set it as default boot loader.
sudo add-apt-repository ppa:rodsmith/refind && sudo apt update && sudo apt install refind && sudo refind-mkdefault
However, when I rebooted the machine with holding down option key (alt), I still got default Mac bootloader with option of EFI boot (which was Linux) and Mac OS option (no rEFInd logos anywhere). I didn't really care until I saw both options in my boot menu.
After a while, when I was strolling through my Mac OS, I saw that I'm starting to lack some memory space, So I just wanted to delete my Linux partition and merge it with MacOS partition. I was stupid enough not to think about boot loader. However, I couldn't merge two partitions together bacause of new Disk utility UI limitations, so I just left it as it is.
When I rebooted the machine, I couldn't get into my MacOS anymore. Holding down option key only gave me
EFI boot option so I installed Linux back on that 70GB partition and formatted it back into Ext4 ( woops, saw no other way around :D ) and thought that I will install rEFInd back and it's all gonna be fine. However, MacOS option now isn't there (the instalation process was the same as the last time, including rEFInd part). Can anyone help me configure my bootloader so that I will be able to access MacOS again? I have no knowledge what is wrong and what/how would I fix it.