Tagging files, not just images

Solution 1:

I would check out Tracker Tags. It's been pretty legit for my purposes

Maybe some more info on the Meta Tracker Ubuntu help page?

You can use extended attributes. You need the attr package.

sudo apt update
sudo apt install attr

Creating a tag:

setfattr -n user.foo -v bar yourfile

Listing tags on a file:

getattr -d yourfile

For GUI, you can use Eiciel

You can add Eiciel to Nautilus and Thunar using custom actions.

For searching, you can use Recoll

Here is a good read: https://www.lesbonscomptes.com/pages/extattrs.html