I replaced my old shredded rubber rear control arm bushings a year ago, first one side and then months later the other side. I was not aware of the history of the non-rubber bushings, I think I have different bushings one side vs. the other, and one set was black and I think the other was a dark red/brown color. One side "creeks" when a ride over a speed bump or torque the frame entering my garage from a step entrance alley.
Is there a difference in brand/type that eliminates the "creeping"?

you may have to pull the arms off and drill zerks into the arms.
this also requires creating grease slots inside the bushings to direct the incoming grease and spread it.

the squeaking is also creating "stickion" or resistance to the movement of the swing arm which drastically changes your effective spring rate and amount of force required to move the arm up/down

it will get worse with time
there will be a point where you will jack the car up and that arm will not fall back to a lower position (even with the pressure of your springs on it)

the zerk technique can solve all of this
don't forget to realign the rear end every time those arms are removed from the chassis

roller bearings or maybe the elephant bronze bushings are another way to solve this

Before I removed my trailing arms, i drilled a 1/4" hole up thru the mount into the chassis, so i could pin them back into the exact position as they were. Also kept track of shims side to side as i only did one side at a time.
Saves alignment if they were properly aligned before

Performance Products and another firm make soft delrin or something like that that do not creak but that means taking everything apart again. The racers put Zerk grease fittings in and the periodically pump them full of grease, sort of like going back in time when you had to grease your old 356

From all I've looked at the $$$ Elephant Racing rear bushings are the closest to stock rubber that's available, but $325 for the bushings, pivot shaft, and install tool, doesn't make it the cheapest option.