I bought a LOT of 3rd party books in 2021. Unfortunately, most of them were kickstarter rewards and even the ones that are complete have been stuck in international shipping hell for months. I'm hoping to at least get Kobold Press's Southlands before Christmas.
Of the (very) few I actually received, Islands of Sina Una is very nice. The art is absolutely gorgeous (except for one inexplicably crude map right at the very start, which gave me a profoundly wrong impression of the book when i first opened it) and it's a D&D look into Filipino stories and myth, which we don't often see in D&D. I LOVE the Tomb Robber subclass - a rogue who broke into a tomb, got cursed, and has slowly worked out how to adapt to the curse and twist it to their own purposes. Really cool. And the five giant epic kaiju god-spirit-beasts who want to eat the moon (and playing a warlock who serves one of them) ... hell yeah to the hell yeah, even thought the 6th level ability is wildly, grotesquely overpowered.
If i had some complaints, the babaylan class looks overpowered to me, too able to hand out large spell DC increases. And the presented setting is a bit too ... idyllic. There's not really much conflict here, all the major spirits have already been appeased by NPCs (negotiating and appeasing spirits is a big deal in the setting), community leaders are generally wise and good and there's little dissension other than some nebulously defined raiders from the sea. A bit more uncertainty and strife and monster-infestation in the setting, and a few pages on how to actually run a campaign in the world and what Sina Unan adventurers actually do and what enemies they might face and the plots those enemies might have (a bit like the excellent section in the Eberron book) would be really really helpful here, for someone who's not familiar with the culture or stories the setting is based on.