Sound Boards

Ambient-mixer.com

Battle Bards sound effects

TabletopAudio Ambient Noise Soundboard

Soft Murmur

Phanary – search for any sound, it pulls from terabytes of sound data released every GDC

Bardly.io – Atmospheres and Sounds

MyNoise.net

SyrinScape

Windows Powershell Soundboard

Realmwalker – D&D Soundscapes (Youtube channel with good background tracks)