I'm currently on a run with very limited mods, just boosting Quality and some QoL Features.

But this mod wierdly doesn't work. My Legendary Yellow Belts still only carry 15 Items per Second. But I can't figure out the issue here :/

I first thought it will only affect new produced belts, but nope.

I have no other mods that affect Belts, like said only some who unlock and boost quality early and stuff like Waterfill, EvoUI, Far Reach and Big Mining Drill Status Lights.

Does this Mod somehow collide with "Quality Assurance" or "Early Quality unlock" ?

Edit: Tried it again with the two Quality mods disabled. Still, not working. I'm out of ideas here :/

I'm not the mod developer,

but the way the belts transform into higher speed ones with quality is dependent on a shortcut tools this mod provides.
These tools are:
"Toggle belt conversion"
"Belt conversion tool"
"Belt un-conversion tool"
They can be accessed the same way that other shortcut items (like blueprints, alt mode, exoskeleton) can be. (using the small button on the top right of your shortcut bar)
They behave like upgrade planners, just select all belts and they get converted and gain their speed.
The only way, besides checking the code, was to check changelog where this is mentioned.

I only found this out when somebody told me this mod crashes with space exploration (icon is nil) with the fix being "icon = base_belt_item.icon or "base/graphics/icons/underground-belt.png", and setting the icon_size to "icon_size = base_belt_item.icon_size or 64,", for all underground belts, splitters and normal belts.

If somebody else had this problem and was looking for a solution, then I hope this helped.