Rather than bugger about with resistors, caps and optos, these can be very effective and require no electrical changes
https://www.aliexpress.com/wholesale...=ferrite+clamp
You can fit them over the mains cables, the motor wiring (make certain all 3 wires go through together though!) and any signal bundles you have in your cabinet.

Note that VFDs are really supposed to be fitted with an EMC filter on the INPUT wiring (L, N & E). Many / most people omit to fit them and wonder why they are finding noise issues. There's no standard size but as long as you ensure it's rated for the max current, you can't go too far wrong. For reference, officially recommended EMC filter on my Yaskawa VFD is the same footprint as the VFD itself.
https://www.aliexpress.com/item/3273...%2315608%23170

I have no experience with any of these suppliers but the products shown are in the right region, technically speaking.