Fix dualboot between OpenCore Sequoia and Linux?

Intel-based Macbook Pro. Did OpenCore upgrade to Sequoia (hooray!). Then shrank the drive and created a new partition (with Disk Utility, while logged in normally) for Linux; booted Linux from a thumbdrive and installed it on that partition (mount point /). Now it will only boot into the Linux partition. Hitting "escape" at startup gets me to a grub command screen. Any way to restore the boot sequence so I can see both OSes as options on boot? Or do I need to start all over, delete everything, and this time use rEFInd?