Hoping someone out there can help... will a front fender from a 2020 Roadglide fit on a 05 Ultra Classic CI?

 

Yep. Should bolt right up. Check tire (fender) width. They put skinny
front tires on Road Glides now.

You will have to do something with the wiring assuming the Ultra
has the fender tip running lamp.

 

Rushmore fenders are not plug-n-play to older tourings. You will need to grind a bit to make it fit. There are lot of RG and SG clean fenders for pre-Rushmore bike available.

 

The shape of the fenders themselves are near the same; however, they mount different and the rushmore fender is slightly lowered.
The rushmore fender has four nuts welded to it's mounting brackets. Bolts pass through the fork lower and engage the fender nuts.
The pre rushmore fenders simply have holes. 4 bolts are used to pass through the fender (from inside the fender) and engage threads located in the fork lowers.

At minimum, you'd have to grind off the nuts...