4dandl4, I’ll definitely try this at least one more time because I’m just experimenting here to learn something and I want it to work. What you describe is close to what happened to me but I didn’t get an option to install grub on the first boot.
Now, Pop OS doesn’t use grub in UEFI and so, in that case, it would not have installed it with the OS and you could still see the same thing I saw - that only Pop OS will boot after installation - and then had the pop up offering to install grub and etc. Is your installation UEFI or BIOS?
The part about os-prober and update-grub I have not tried yet but I will and report back here. Might be a couple of days. I also need to discover how to turn off encryption by default. Encryption is good stuff but not, probably, in a dual boot setup.
What can you tell me about whether you are in UEFI or turning off encryption?