Pre-UEFI they were fighting over the boot sector, sure, but now that everything is more well defined, and every OS can read the FAT32 ESP? Never seen it…

At worst the UEFI boot entry is replaced. There are some really shitty UEFI implementations out there which only want to load \efi\microsoft\boot\bootx64.efi or \efi\boot\bootx64.efi, or keep resetting you back to those.

Assuming you were dumped into Windows suddenly, you can check if you have the necessary boot entries still with bcdedit and its firmware option

bcdedit /enum firmware

If you just have a broken order you can fix it with

bcdedit /set {fwbootmgr} displayorder {<GUID>} /addfirst

If you actually need a new entry for Linux it’s a bit more annyoing, you need to copy one of the windows entries, and then modify it.

bcdedit /copy {<GUID1>} /d "Fedora"
bcdedit /set {<GUID2>} path \EFI\FEDORA\SHIM.EFI
bcdedit /set {fwbootmgr} displayorder {<GUID2>} /addfirst

Where GUID1 is a suitable entry from windows, and GUID2 is the one you get back from the copy command as the identifier of the new entry. Of course you will have to adjust the description and the path according to your distro and where it puts its shim, or the grub efi, depending on which you’d like to start.

Edit: Using DiskGenius might be a little more comfortable.