@bagder maintainer burnout is imho the biggest one at the moment. it lead to the xz situation amongst many others this year after all.
Finding young developers can be very difficult as well i bet - frontend frameworks and other javascript projects probably have it easier finding young people, but projects written in C probably have a harder time. My apprenticeship didn't teach me anything about computers or any non-OOP language, let alone anything without a garbage collector. Anything I learned about how computers actually work, and C, was either a little bit in my A-levels, or completely self-taught. Knowing how computers work, what memory management is, etc, is exceedingly rare to find in younger developers, which is sad to see. I bet plenty of these would love to learn about these topics in their apprenticeship as a software dev.
AI-slop will probably be an increasing issue in the future i bet; you have to sift through more garbage and try to distinguish from ai-generated crap from real issues/contributions, without accidentally throwing something out because a non-native speaker used an llm to translate his text.
One positive thing's for sure, foss devs ain't gonna run out of things to do!