sgtlion [any]

I would look at BIOS secyre boot/boot mode options. And depending on the age of the PC whether it supports UEFI or you need a legacy boot.

Yes. May need to turn off secure boot too.

Are they installed on separate drives? Depending on the exact setup, Linux and windows both generally support legacy as a boot method, so you may be able to just BIOS to select a boot drive.

Honestly, IRC was a very functional, easy, free, low-resource and privacy friendly chat protocol and I don’t really see why it got left behind. If you wanted image/ file support that could really be implemented client and/or server side.

You can’t trust any of it to be totally secure, it’s effectively impossible. But, this is true of all software, at least open source is being audited and scrutinised all the time (as demonstrated).

All you can do is follow best practices.