I think the limitation is the size is the look up table , held in ram not the size of the data. So for instance a 30 minute symphony might be 1 entry ,whereas old singles at 2 minutes duration each are also entries. My Sony NWA with 128 GB sd card, has about 6000 entries ,but some of these are single flac files of entire digitised albums ,which take an hour to play.I'd like an answer to this question. It seems that nothing is made for people like us. I have just under 30,000 files in my music collection, about 400 are full albums approx 311gb's. Been trying many DAP's. Shanling's latest Q1 won't finish updating library past 15,000 files without failing. Fiio is the same. Hidizs AP80 stops at 20,000 - no more. iBasso dx50 with latest update reads card and plays but no way to know how many files, it never informs you. It sucks that everything is made for the 87%. Us 13%'ers aren't enough of a market for anyone to care about it seems.
HiBy Music 3.0 is run by several players. I'm using a Hidizs AP80 Pro with HiBy Music 3.0.Hi. Don't know if you are still looking for answers to this but ... entry-level Sony hi-res player, NW-A50 series, database can catalog >20k tracks and the player accepts 1TB microSD. The A50 series runs Sony's proprietary OS.
Also, while this might not be exactly what you want, HiBy Music 3.0 supports browsing by folder & file name. This gets around 20k DB limit.
The Fiio M6 works fine with my collection of 70,000 mp3 tracks (on a 512GB MicroSD card). The same collection, on the same memory card, also works fine on my phone (Moto G 5G). I use an app called GoneMadMusicPlayer, which seems to be good at handling very large music libraries.