Hi,
Recently I shared on this forum my problem with dual-booting Windows 10 and Solus. The problem exactly was that my BIOS did not allow me to change the boot order for the two OSs installed on one drive. And Windows always came first. I wanted Solus's boot manager to be the default one and include Windows.
I tried out several options and they did not work. I even tried creating a separate partition for Solus's boot manager, copying W10 boot manager there, and deleting the Windows boot partition! It worked for a few days and then stopped working for an unknown reason -- I did not even update either OS at that time.
I would like to share a solution I have found. It is simple and includes these steps:
(1) Make a clean install of W10 on a formatted disk, with default settings. Just in case - update Windows right after. Do not change partitions at this point. If you do, you won't be able to complete the next step, as the needed installation option will likely disappear.
(2) Install Solus from the USB stick. Choose the option which reads something like that: Install alongside another OS. Update Solus.
(3) Now, the secret sauce part. Boot up Windows again and install the program called EasyUEFI. Start the program and choose the boot order as described in this video at 4 min 00 sec. Thanks to the user Tech Seedr for sharing this method.
Again, it is easier to change the boot order in BIOS. If you are able to do this, or if Linux's boot manager starts as the default one, you don't really need this method.
That's all.