Both of these are very consistent and good open source emoji. I think in the past a lot of these projects that were not backed by companies eventually devolved into a paid product that was no longer open source, but I'm hopeful that openmoji continues down the FOSS path.
JFTR, "Symbola" font[0] actually is not an opensource and just freeware for personal use, but it was "fully free for any use"[1] till February/March 2018[2].
BTW, Even in actual state "Symbola" is my fav font for emoji input on desktop (via Gucharmap[2]) and mobile (via UnicodePad[3]).
Looks like Google’s aren’t super easy to use outside of Chrome and Android:
> NotoColorEmoji uses the CBDT/CBLC color font format, which is supported by Android and Chrome/Chromium OS. Windows supports it starting with Windows 10 Anniversary Update in Chrome and Edge. On macOS, only Chrome supports it, while on Linux it will support it with some fontconfig tweaking, see issue #36. Currently we do not build other color font formats.
Twitter emoji (discord uses these also) are open source: https://twemoji.twitter.com/
Both of these are very consistent and good open source emoji. I think in the past a lot of these projects that were not backed by companies eventually devolved into a paid product that was no longer open source, but I'm hopeful that openmoji continues down the FOSS path.