You can install as many OSes as you want.
Odds are your Linux install overwrote OCLP. You'd need to install OCLP again and configure it to boot from either Mac OS or your Linux install.
And with GPT partition you can have 128 partitions so ~120 different OSes easily on a single drive.
Even more with btrfs or LVM.
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.
If they all support EFI, you'll be out of disk space before you hit the limits of EFI partitioning.
Unless you're one if those challenge accepted people who will try installing 10,000 floppy drive-sized microlinuxes on one system.
We're assuming useful daily driver desktop as the benchmark here. Not boot to a console with nothing on it.
OSX doesn't seem to play nice with linux dual booting. I think holding the option key while booting should force the apple boot menu to show, at least it did when i tried.
You can always chainload bootloaders and have grub or refind pick the linux os
OP is using OpenCore Legacy Patcher to run an newer OS on an unsupported machine. The option boot menu won't work, they'd need to get back to the OCLP menu to boot Mac OS.
Probably when you installed the second linux you overwrote the boot loader instead of adding a new UEFI entry point.
But I've never had a Mac, so take this with a pinch of salt, and honestly considering things can change based on what, in which order, and how you installed things.. it could be something else.
you've got a grub bootloader in the efi partition. the computer is booting the efi partition's grub straight out of the gate. it doesn't know about the macos so it can't boot to it.
you can edit the grub config to put an option in to boot to macos from grub but you can also just use option-boot to select partitions when you power the computer on.
option-boot is when you hold the option key when you turn the computer on.
Did you choose the right partition?
Do you still see your Mac partition when you do fdisk -l?
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