Yes, the Gigabyte H110M-H motherboard supports UEFI. Your i5-7400 CPU is also compatible with UEFI.
Regarding your question about converting your boot drive to GPT, it's definitely possible. However, there are a few things to keep in mind:
1. Before converting, make sure that your motherboard's firmware is set to UEFI mode. If it's set to Legacy BIOS mode, you won't be able to boot from the GPT drive.
2. Converting your boot drive to GPT will erase all data on the drive, so make sure to back up your important files before proceeding.
3. You will need to use a third-party tool to convert your existing MBR disk to GPT. Windows has a built-in utility called "MBR2GPT.exe", which you can use to convert your disk without losing data. However, this tool has some limitations, so you may need to use a more powerful third-party tool like EaseUS Partition Master or AOMEI Partition Assistant.
Once you've converted your boot drive to GPT, you should be able to install Windows 11 without any issues. Just make sure to select the UEFI boot option during the installation process.