Everything you do on your own instance is against a cached version of the original post that is saved on your instance. Your instance sends updates in the background, the other instance can be entirely down and you can still browse, comment, and vote as normal on your own. The updates will just stay local though.
It doesn’t. Even if you defederate with an instance, you can still comment and vote on posts from that instance that predate the defederation and people on your instance will see them, it just won’t go to the original one.
It is a very typical way of doing things, you just have to read the output and make sure no important packages are in the list.
Your command should be working. It won’t remove manually installed dependencies but should take care of automatic ones. You can check an individual package with apt show and look at the APT-Manual-Installed field.
If you use Obsidian for work you generally need to pay for the commercial license, with some exceptions. I like to mention it because people grab it from flathub without reading the license terms. This is not including the sync fee.
Many hobbies have some sort of cost associated, I would hope materials to do the hobby aren’t necessarily seen as negatives.
People have been doing HAM radio (and learning it), electronics tinkering, woodworking, fishing, etc for ages. There are upfront costs to get equipment, although used stuff abounds, ongoing costs are materials or components that one wants. For some things once you get it working you don’t necessarily have ongoing costs.
I see commercialism as exploitive, just purchasing things not so much.