Can't see my buddy on my own AdhocServer

[LunaMoo]

As far as I understand, if you're connecting through router, then you have to forward those ports on the router, same for your friend. Linux or what else you're running the server or clients on, doesn't matter unless you have a software firewall that also needs to allow ppsspp to connect.
PPSSPP could port forward using UPnP, but someone with specific knowledge has to code it and most of the time we don't have anyone working on adhoc at all, it's also very messy compared to rest of the project and likely not too inviting for new developers:].

In case of PPSSPP adhoc feature, linux gives no advantage, in fact puts you in disadvantage compared to windows due to not allowing ports under 1024 which psp games often use. That requires elevated priviledges or port offset which AFAIK still have some bug found recently, but lucky for you, MH games aren't affected.