Which Icon theme were you using prior that included the Tutanota and Freetube icons?
You can use that as a reference to know what naming convention to use - then create or find icons to match your existing theme and name them by that convention. Include copies in your icon theme apps folders.
It is better to resize the image to the size designated by the folder.
This is entirely up to you.
I started out the same way- just trying to fix an icon set.
Now, I make my own full sets.
Freetube and Tutanota are not common icons... No matter what icon set you use, there will always be some missing.
So it helps to get used to adding your own from time to time.
It becomes very easy once you know what you are doing.
If you are saving a file that is in a raster format, like .png and you want to save it as an .svg, you must convert the file.
You can use a simple terminal command to do this on Zorin OS since Zorin OS comes with imagemagik installed. Run the terminal command from within the same directory as the the files:
convert example.png example.svg
I use Inkscape as a graphical editor for .svg files. Inkscape is a versatile and powerful app.
Inkscape includes cli commands as well and the list is extensive.
But... If you install Inkscape, you can convert using the GUI save function.
Open a .png in Inkscape, then save it as an .svg
You can also open .svg file in Inkscape, then export it as a .png image File > export > png image or shift+ctrl+e
@Storm taught me a much better and more organized method - and one that saves space (bloat) and is simpler to work with.
To use as a template, you can download one of Storms icon sets (I Like Mistique set)
Yes, actually the update had a 404 error for conky. Didn't know it prevented actions following it.
Err:25 http://ppa.launchpad.net/mark-pcnetspec/conky-manager-pm9/ubuntu focal Release
404 Not Found [IP: 18.104.22.168 80]
E: The repository 'http://ppa.launchpad.net/mark-pcnetspec/conky-manager-pm9/ubuntu focal Release' does not have a Release file.`
I'll have to figure out what to do about that. Thanks for clarifying.