Need help identifying sports/bugs/shrooms(?) on my indoor plant

Hello everybody,

I'm fairly new to this sub, so I apologize in advance if I'm not posting correctly, please feel free to correct me. 

I've recently noticed those weird beige volumes with a brow center appearing on many leaves of my plant. It has taken time for me to notice them because they seem to be especially located on on the back of the leaves. I've tried several Google searches but I've been unfortunate so far, at first i thought it could be mealybugs but now I don't think so. They seem to come with a bit of dust on the leafs – even though it's fairly difficult to say because it's mostly on the lower leafs, so it could be regular dust.

I've had this plant for two or three years now, and only noticing this. Obviously I'm quite attached to it, so I'm pretty worried.

I would really appreciate if any of you had a guess – and maybe an idea for an ecological solution against it ?

Thank you in advance