Is this a Linux KiCad 7 Bug or something I am doing wrong

It's not clear to me what your actual problem is.  You say missing field, but what missing field?  Is the top image 7.0.6?  It looks to me that instead of having the net filters, you do it by creating a pattern and it shows all the nets that match that pattern and you assign the net class to it (and thus the matching nets.)  

The net class filter UI changed in KiCad 7. Bluntly, I find the new design very unintuitive.

The list of nets is no longer shown. Instead, as a human with vastly more memory and processing capability than your computer, you must memorize the net names (especially the internally generated ones) to type in the pattern you wish to match manually. And don't worry; it has to be an exact match or one with undocumented wildcards for extra difficulty! Although astrix(*) tends to work, sometimes, but not others. For some reason.

(Totally valid, in my opinion,) Sarcasm aside, that is how KiCad 7 works now.

Really???  I've not changed yet, but good Lord.

I'm not following the thread or the sarcasm.

So this is normal for version 7?

Yes. The UI/UX was changed in version 7 to what you see now.

There is no longer a list of available nets (in that dialog).

You have to know the name of the nets before you setup the filter.

Manged to weed my way through. Talk about a step backwards. The netclass sizes now work.

The scenario of missing fields I have in another program called Inkscape. It happened after an upgrade. I made the same assumption with this.

Thanks for chiming in. 

After closer examination I discovered the Pattern GND connections picked up the Net Class of Power and applied the desired the assigned track width. The Pattern +5V would not pick up the desired track width and used the default. I could right-click customize the +5V track width to the required length but it would not work with the Net Class.

I did have this working on KiCad 6 but this is my first real end-to-end test of 7. I'm not sure why net class works for GND and not +5V:)