I have a ton of purple bubble algae as well.
Tried the same things, with little luck.
My latest approach did seem to be working though. While it is far from gone, it is not growing as rampantly.
The key issues I believe are lighting and nitrates.
BTW: Nitrate testing will not help. You will probably test out at 0 like me. The bubble algae is eating it.
Step 1: Stronger light, with less yellow and red in it.
Changing the bulbs led to an immediate reduction.
An experiment with fairly warm colored LEDs unfortunately increased it.
Most of mine is now at the bottom or semi-shaded areas.
Step 2: Consider an algae turf scrubber.
Basically, you deliberately grow green algae on an easily removable screen, and scrape it
off every week. They are great at nitrate removal.
Unfortunately, they are DIY, and have to be really well built to out-compete bubble.
But it is probably the only "filter" that will starve it out.
Alternative: Consider living with it.
It is really rather pretty unless it completely takes over. And it does add diversity and extra food.