I’m experimenting with a 2014 macbook pro upgraded to macOS 14.4 (Sonoma) with OpenCore Legacy Patcher, Linux Mint 21.3 Virginia and Linux Mint 21.3 Xfce.
First, I installed Linux Mint 21.3 Virginia and I could boot both to macOS and Mint. Then, I created another partition and installed Mint Xfce on it.
Now, I can only access both linux operative systems and macOS has disappeared.
What I don’t understand is why now the notebook boots directly to grub instead of booting to OpenCore Legacy Patcher
Yes. It mostly comes down to two things: Bootloader and partitioning schema.
A properly configured bootloader should include an option for all of your OSes. In most cases, any installed OS should be autodetected an added to the menu. If not, as long as you can boot at least one linux distro, adding any missing ones isn’t that hard. I suspect that in your case, the latest OS install didn’t account for the missing OS during grub setup.
Partitioning schema isn’t hard either, but it can be a bit hard to keep track of the various partitions during install. Just make sure that each OS gets its own partition(s), and that you don’t mistakenly overwrite any during install.