I’ve made offline iconify iconset which contains only below iconsets:
- Material Symbols, iconset
material-symbols - Google Material Icons, iconset
ic - Material Design Icons, iconset
mdi - Remix Icon, iconset
ri - Carbon, iconset
carbon - Unicons, iconset
uil - MingCute Icon, iconset
mingcute - Memory Icons, iconset
memory - Unicons Monochrome, iconset
uim - Unicons Thin Line, iconset
uit - Unicons Solid, iconset
uis - IconPark Outline, iconset
icon-park-outline - IconPark Solid, iconset
icon-park-solid - IconPark TwoTone, iconset
icon-park-twotone - IconPark, iconset
icon-park
(they are licensed under Apache and fit into “general” category).
Attached link is ~30 megs, so it may slow down startup of your system https://co7.io/CFHi ;-).
Icons are available via two paths: /icon/baseline_1k.svg?iconset=ic, in schematic it is <icon>.svg?<icon-set>, or using classic iconset with scheme <icon-set>-<icon>.svg.
If you request icon containing _ it will be replaced with -. Assuming above example of baseline_1k or ic_baseline_1k final icon request will be baseline-1k or ic-baseline-1k.
This is due to two facts first 1) special meaning of dash for dynamic icons, 2) assumption that classic is default iconset (its hard to override it through UI config).
Note, using above icons will make main ui freak and display no icons. At least that was case for my test setup. Anyone interested in testing this - feel free to play with it. 
Sources as usual available here: connectorio-addons/bundles/org.connectorio.addons.ui.iconify at master · ConnectorIO/connectorio-addons · GitHub
// edit 20.02.2023
Marketplace entry with provider: Iconify icon provider.