It could be anything from tutorials, YouTube channels, plugins/software, anything goes for this first post.
One of the most recent things I've stumbled across recently was Baphometrix's Clip-to-zero series. While I don't work on music that needs to be competitively loud, the in-depth series helped provide a new perspective to incorporate into decades-old mixing habbits.
Link to the playlist:https://www.youtube.com/watch?v=5UT42-ur080&list=PLxik-POfUXY6i_fP0f4qXNwdMxh3PXxJx&pp=iAQB (I didn't watch every episode)
I also really appreciate the work Dan Worrall is doing these days: https://www.youtube.com/c/DanWorrall
For finding samples I always used freesounds.org but a friend of mine recently turned me on to Splice, it's a good way to get professional sounding sample packs and individual sounds based on a subscription model.
Another cool resource that is free is the synth plugin Vital. It's somewhat comparable to serum or massive, very in depth modern wavetable synth with a ton of routing capabilities and onboard effects. Highly recommended!
Never heard of Vital… will check it out as a heavy Massive X user. Thanks!