I use language tool for that in libre. Works great!

Krita has a Windows version.

Not having Firefox, or a derivate, I’d rather use Chromium.

Zoho is a good alternative.

That’s a 404 …

I think, I can install keys in my AMI bios. So, basically, I’d create some keys, sign the kernel with it, reboot, install them keys in UEFI, enable secure boot, and, fingers crossed, I’d boot?

Stable just means no major version jumps in software that might break your current setup. That’s important for operating servers, not desktops.

I use debian Sid (unstable) at work and never had problems. Most of the time I get updates prior to other distributions I am using.

At home I use arch (derivates, manjaro), with great success.

I would abstain from Ubuntu. There, I had problems, it is very opinionated and not in s good way.

In a general sense I would always chose a distribution that isn’t too locked in to a certain desktop environment and provides updates, quickly.