Excuse the long post; just trying to be as clear as possible. Initially, I used bootcamp to install Windows 10 alongside Mac OS. During restart, it would automatically boot me into Mac OS and whenever I needed to boot into Windows, I used to hold the option key while starting and that gave me the option to boot into either Windows or continue with Mac OS.
After using it for a while, I decided to try out Ubuntu 20.04. So I partitioned my Mac OS Volume and installed Ubuntu manually. Even though I was successful, I realized that I could no longer boot into Windows anymore. Auto boot was changed to Ubuntu and if I held the option key during restart, I used to get an option for booting into Mac (working) and Windows (this too was not working).
Here is where I actually messed up. Today I decided to retain the unused Windows partition space and hence, booted into Mac OS and deleted the Windows partition using bootcamp and did a restart. Now I'm unable to log into Mac OS. Auto boot is still set to Ubuntu and no option is shown when using the option key.
I know that I can do a complete reinstall but just wanted to know if there is any way to regain my Mac OS boot option without a complete restore? Currently, Ubuntu is working fine.
TL;DR: Initially installed Windows 10 using bootcamp in Macbook pro. Decided to triple install Ubuntu. Succeeded but lost access to Windows partition. So decided to free that space with bootcamp and now lost access to Mac OS. Is there any chance to recover the boot option for Mac OS without complete restore?