Not a big hardware guy but I assume you already know about hackaday.

https://hackaday.com/

I like hackaday too, but a lot of their content is just farming from other sources like youtube. Its a cheap way to make content without doing much good quality work. All3DP is the same with 3d printing, their content academy is literally about paying “writers” to do the work for peanuts.

I like this list: https://github.com/aolofsson/awesome-opensource-hardware

https://www.crowdsupply.com also has a discord channel

All the supplier catalogues: rswww, farnell, mcmaster in the US, etc.