Don’t confuse backups with syncing. Although syncthing has a recycle bin to recover deleted and overwritten files, you shouldn’t rely on it for guarding against accidental deletion, file corruption, or ransomware. You want something that will allow you to restore files from a point in time. There’s lots of proper backup tools for this. Borg, Restic, etc. Each has pros and cons. Make sure you test recovery. Also 3-2-1 is 3 copies of data, on at least 2 different systems, and 1 off site.

Static site generators. Jekyll, Hugo, etc. Pick a template, write in markdown.

Homebox? Create an asset for, say, your furnace, then you can create maintenance tasks, with dates and costs, and schedule future work.

You need to figure out your threat model. Is it that you don’t want YouTube to connect you to what you watch? Is it okay that YouTube knows that soneone at your IP watched the video? What about intermediaries knowing who you are or what you watch?
Most of these options just avoid using Youtube’s UI, which at best blocks cookies, but reveal your IP. Others download, which is about the same.

Been using Garage for non critical stuff for a while, no problems.