Signal cares so much about UX that they're starting to agitate security/privacy diehards. They've implemented features like stickers and message reactions that the diehard community calls "useless". And they recently implemented PINs with the intention of storing your encrypted profile and settings for easy recovery on a new device.
I applaud the direction they've taken. These are the kinds of features that will acquire and retain a broader user base.
Not sure what you’re looking to get into specifically but here’s some resources you can look at in no particular order:
Hack the Box
Try Hack Me
Pentester Lab
Hacker101
Portswigger Web Security Academy
Linux Academy
Bugcrowd University
Hacksplaining
Cybrary
Malware Unicorn
bugbountyguide.com
CTFtime
root-me.org
MalwareTech
Nahamsec
The Cyber Mentor
Not quite yet. But also like another user said, DuckDNS
"Note: Starting January 1st, 2020, GCP will charge for VM instance external IP addresses. However, under the Free Tier, in-use external IP addresses will be free until you have used a number of hours equal to the total hours in the current month. Free Tier for in-use external IP addresses apply to all instance types (not just f1.micro instances)."