Yes, Rubber can be taken off to make an open bearing.
Metal shielded bearings shields can also be taken off to make it an open bearing.
For metal shielded bearings use a pick and poke thru the metal shield then pop it off.
Rubber shields can actually be take off, grease added then the rubber shield can be put back on.
I realized this when I popped a RS bearing open
I was surprised at how little grease is actually used in a RS or ZZ bearing.
I never actually added grease to a RS or ZZ bearing. I just trust that it's got grease in it.