Hi,
v1.20 is released with new mappers and fixes.
nesos-v1.20 23.12.2019
1) OS naming convention was changed to make clear differentiation between PRO and OG N8 OS. OG N8 OS is 1.xx and PRO is 2.xx
2) Now save states supported by all mappers.
3) New fully functional MMC5 mapper
4) New FDS audio core
5) Audio core for Sunsof5 mapper by Necronomfive
6) Audio core for VRC7 mapper by Necronomfive
7) Specific games databese update. Now works few more games which require specific settings

Minor update from MMC3
9) New mappers support(1): 27, 30, 50, 106, 108, 142, 144, 145, 149, 156, 165, 171, 175, 176, 183, 213, 216,
9) New mappers support(2): 222, 252, 37, 45, 49, 51, 52, 105, 177, 190, 197, 207, 214, 228, 229, 244, 249, 250,
9) New mappers support(3): 35, 44, 56, 60, 103, 117, 132, 136, 143, 159, 172, 173, 183, 186, 187, 198, 199, 221, 238, 248
10) FDS autoswap blocking function. Hold A to prevent disk swap. This is mostly for test fds sound in zelda intro.
11) Fixed irq counter in Acclaim mmc3 mapper
12) Audio balance option for mappers with expansion audio
13) Some mappers and fixes were back ported from N8-PRO