It’s important to note that you need an internet connection to fetch the icons initially from https://api.iconify.design , so you need to trust the service as well. If you don’t, or want everything locally, I’ll provide an alternative below.
Both things can change any time. You are hosting your own service but making it dependent on others.
What if I don’t want to rely on a remote service to display my icons?
You will have to use almost same icon for all your appliances or make new widget (with hard coded icon) for each one. Isn’t?
Please see the icons from my links. There are many more useful icons there, much less than in iconify but without comparison more than in F7 and current material.
The zip file you can download there is 2.1MiB
The F7 and material icons are in font form?
If so, isn’t it enough to replace three or four files in the org.openhab.ui-x.x.x.jar file
Is there anything else that needs changing?
Please understand that the internet is full of free icons but using them requires time to find and use them properly.
As it was nicely done in HABPanel.