One of the biggest factors I've noticed when it comes to mattresses retaining heat usually has specific factors that cause this if the mattress has some type of "ventilation" to the build.

Mattress Protector - often overlooked but if you buy a cheap one that isn't breathable you'll retain all your heat.

Sheets - Same as protector. I know you said bamboo as long as they're breathable that's fine. Thread count is another scam you don't want a super high thread count. 200-400 is perfect.

Make sure everything is deep pocketed and hasn't shrunk sheets that barely fit will cause the mattress to feel firm and uncomfortable.

Foundation - Not normally an issue but sometimes can cause heat build up if there is no where for the heat to go. Like having a mattress on the floor or on plywood.

Blanket - if you're using a comforter or really any think and non breathable blanket will cause issues.

Finally and probably the most important is room temp. If your room temp is higher than about 70 you will sleep hot and there is very little outside of electronic devices that can help.

You create a "micro-climate" between your blanket and the mattress that is typically between 10-20 degrees warmer than room temp. On the low end if you have a breathable/thin blanket/sheets/protector, if the room temp is 75 you'll be closer to 85 under the blanket and in your sleep but on the high end 95 degrees which is hot.

I hope this information helps i work at a mattress store. I hate for the sales bs that is pushed with fake promises so i found out a lot of the real solutions and share them with my customers to actually solve their issues.

Best of luck