This thread has a lot of language suggestions, but I think you need a fun problem to solve. Pick a toy app and work on it. Learn embedded programming with an Arduino. Write an iPhone app to track when you feed the dog. Make a karaoke app for Android. If you pick a project you'll enjoy, the language won't matter. Use whatever is best for the platform. The fun doesn't come with the language, it comes with seeing your project come to life, or others' reaction to the cool thing you made. Every language sucks and every language is the best depending on who you ask. Don't focus so deeply on that part. Solve cool and fun problems.
I've had a long time dream of getting a broken jukebox and gutting it for a Raspberry Pi, but keeping the external interface in tact. I know next to nothing about hardware engineering, and can't write more than ten lines of Python without needing to Google something, but I finally got a broken juke in need of fixing, a multimeter, and a hard drive full of music ready to go. The fun isn't the Python or learning GPIO, it's that eventually I will have a cool retro jukebox with hardware and software I wrote in my basement.
Big +1 on this. If you're OK with a broader definition of "programming" and have a bit of money to throw around, I've found tinkering with https://www.home-assistant.io/ to be very satisfying. I got more sense of accomplishment from scripting "text me when I leave the house if I forgot to set the alarm, and turn on the front porch lights when I arrive back if it's after sunset" than I did from months of corporate work, even though the actual _difficulty_ was much lower. I can _see_ the results of my work, and benefit from them most days!
Deploying Home Assistant is largely how I taught myself Docker, Kubernetes etc. Its much easier to learn solving a "real" example.
You can learn a ton just trying to do a production grade home assistant deployment - move on to SSL termination at the load balancer with letsencrypt, try different deployment strategies for upgrading the server with zero down time, write custom extensions... etc etc.
I've now got a small Pi cluster running k8s to deliver a bunch of services at home, and its all really easy to maintain. I've absolutely used the skills and knowledge gained in my day job too, which is nice. Home Assistant is great to learn a lot of production web app stuff, all you need to get started is as little as the PC you already own, or something like a Pi to host it. As it can solve problems in your actual life, it's rewarding enough to be interesting I've found.
Homeassistant is such a useful project. I use it for self hosting bitwarden, ubiquiti addon and bunch of smart home devices. For SSL I have been using local root authority but is a pain to maintain. I am able to access HA client from browser and Android phones but iPhones don't want to play. How did you do LetsEncrypt with HA?
https://en.wikipedia.org/wiki/Reverse_proxy
If you use LetsEncrypt's DNS-01 challenge to setup the SSL automatically, you can even deploy valid working SSL for IPs in the private range (192.168.x.x, 10.x.x.x etc etc), allowing auto-deployment of SSL for private services on your LAN, not just publicly accessible/exposed IPs. You can get around port forwarding during initial letsencrypt setup with this too, as all happens via DNS providers public APIs.
> https://letsencrypt.org/docs/challenge-types/#dns-01-challen...
Caddy is really easy to deploy as a Docker instance as well. There are many, many ways to accomplish LetsEncyrypt with HA though! It's really just an example of a common generic reverse proxy problem - searching for "reverse proxy letsencrypt" will show you many other ways to do it too. If you are using Docker to host your services at small scale, there are some really clever options now that auto-configure Caddy and SSL via letsencrypt all just using docker compose: