UEFI Boot Issue Resolution

I'm seeking an experienced Linux and UEFI specialist to troubleshoot a boot issue. My system currently boots into Ubuntu without giving me the option to select Debian or another partition.

Requirements:
- Check UEFI settings and boot menu
- Diagnose and resolve the boot issue
- Ensure all OS options are accessible at startup

Ideal Skills:
- Strong Linux knowledge, especially with UEFI
- Experience troubleshooting multi-boot setups
- Familiarity with Ubuntu and Debian

Please provide a brief overview of your relevant experience and approach to this problem.