I don't know if I have favorite resources to recommend. I know there are a ton of YouTube videos and podcasts that offer a lot of good ideas. I like reading the Linux Kernel Mailing List and tech notes.

Simply buying any one of the cheap boards you can find online (if they have supply) and trying to get something like a JTAG debugger working will be beneficial to you. Just try to get something simple going on bare metal. It's been a while since I worked with PIC microcontrollers, yet as I remember there is a lot you can do with some of the cheap PIC devices, a breadboard, and an investment of $100 - $200 in electronic parts. It was important for me to build up a modest lab of electronic test equipment, power supplies, breadboards, etc.

Wishing you success, whatever route you go.

Buy a few ESP32 boards and make an LED blink. Once you get past that, the sky is the limit.