I haven’t found the point of “added support for the FP5”. Maybe I’ve missed that. But AFAIK the easy installer still doesn’t support FP5 unfortunately (so I think the list of devices is correct).
Correct.
I wouldn’t express it like that. I’d rather say "you’ve to enable developer mode to enable OEM unlocking there. And if you closely follow the instructions you’ll also need ADB debugging, which you also find the the developer mode settings.
I think your Linux Mint should already contain “fastboot” and “adb” (I assume these are the “third party tools” you’re referring to). If not you can install them using the Mint packet installer.
Agreed. Keep asking in case of more doubts!
I don’t think so. If you are ok with the decision of not relocking your device (and always deny that, in case you phone might ask for relocking during the installation process), then I don’t see major risk.