Blender

OpenSCAD. 3D modeling as code.

I’ve gotten a lot out of it, and their tutorial is excellent.

One thing I want to learn which seems important to me career wise is HEC-RAS, a hydrological River Analysis Software. I think it’s free?

From this you can build your own predictions of when flooding (or drought!) will occur in your local area

Learn the basics of a couple of FOSS audio-software staples.

LMMS - tracker

Audacity - Audio recorder

Godot. Start with an idle game, move onto more. Just don’t make a horror game, way too many of those and a lot of them are bad.

My suggestion already submitted was Blender, but any of these ideas require a purpose. I don’t think you truly learn an application or language (even human languages!) if you don’t have something you’re trying to do with it. Even music (it’s a language), you can learn how to play something, how to put together notes and sounds, but you really start figuring out how to do things when you have a need to accomplish.

I would say 90% of my coding and application knowledge comes from decades of having a need or inspiration to do something, and having to find the right tool and learn how to use it to make my idea become something (even if it doesn’t get finished). When that purpose or desire disappears (for whatever reason) I stop wanting or caring about learning more about the tool I was using to do it with.

Your initial request seems to point to a different style of learning, wanting to do it for the journey itself. That’s cool, I just wonder if you had a reason for doing it, would it make the effort more fun and worthwhile.

Since you already recorded something with OBS, you could try your hand at video editing with something like kdenlive

Meshtastic (Software and hardware).

• MuseScore 4 is a (the!) free music notation software. It is genuinely fantastic. It’s also a lot of fun, if you know some notation basics and want to play around.
• Darktable is a Raw photo editor in the vein of Lightroom. Except where lightroom is sleek, polished, user friendly and Adobe (🤮), Darktable is FOSS, and clearly so both in the design and functionality: it could easily make a UX designer cry, but if you’re willing to give it a try, there does not exist a more potent raw editor on this earth. Lightroom is a toy in comparison. (Now whether you need that is another question… But I’ve been using it for more than 10 years, and am still finding new, incredibly useful sub-menus, drop-down contexts on hidden sliders,…)
• rmpc is a really cool TUI music player

Python, and you kind of want to take the long way around.

Get it up and running in its own virtual environment. On Linux and Windows this’ll just be a directory its in, and once you’ve activated that install via a terminal command everything stays self contained. It has a package manager called “pip” that will handle package and dependency management. Use pip to install spyder, pandas, matplotlib, numpy, scipy, and openpyxl. If you install anaconda this is what it’s doing under the hood, but there are licensing hiccups with using their package repos.

Anyway, however you get up and going, numpy is fast numerical storage, scipy is a lot of scientific algorithms, pandas is a data analysis library that rides on top of numpy, and openpyxl is an interface to excel files from python. Pandas will get you one line CSV file reads and writes and more complex manipulation of Excel spreadsheets. Openpyxl gets you cell by cell manipulation of a spreadsheet. Spyder is a development environment.

It can do much, much more.

I asked an LLM for a small python example with pandas and matplotlib. Load it into spyder and run it and see what happens (tip, go into the settings/preferences, IPython Console, Plotting, and change the Graphics Backend to “Qt” to get the plots in their own window).

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

def generate_damped_signal():
    # 1. Setup Parameters
    fs = 50                 # 50Hz Sampling frequency
    t_max = 6.0             # Run for 6 seconds to clearly visualize it hitting 0 at 5s
    freq = 2.0              # Oscillation frequency in Hz
    
    # 2. Generate Independent Time Axis
    # 50 samples per second from 0 to t_max
    time = np.arange(0, t_max, 1/fs)
    
    # 3. Generate Dependent Damped Signal Axis
    # Using an exponential decay constant of 1.0 ensures that at t=5 seconds,
    # e^(-5) drops down to ~0.006, effectively decaying the signal to zero.
    amplitude = np.exp(-time) * np.cos(2 * np.pi * freq * time)
    
    # 4. Create Pandas DataFrame
    df = pd.DataFrame({
        'Time_Seconds': time,
        'Signal_Amplitude': amplitude
    })
    
    # 5. Export DataFrame to CSV File
    csv_filename = "damped_signal.csv"
    df.to_csv(csv_filename, index=False)
    print(f"Successfully generated DataFrame and saved to '{csv_filename}'")
    
    # 6. Plot the Data Using Matplotlib
    plt.figure(figsize=(10, 5))
    plt.plot(df['Time_Seconds'], df['Signal_Amplitude'], label='Damped Signal', color='cyan', linewidth=2)
    
    # Visual Anchors for the 5-second decay mark
    plt.axvline(x=5.0, color='red', linestyle='--', alpha=0.7, label='5-Second Decay Target')
    plt.axhline(y=0.0, color='gray', linestyle='-', alpha=0.5)
    
    # Labeling and Grid Configuration
    plt.title('Damped Signal Decay Over Time (50Hz Sampling Rate)')
    plt.xlabel('Time (Independent Axis - Seconds)')
    plt.ylabel('Signal (Dependent Axis - Amplitude)')
    plt.grid(True, linestyle=':', alpha=0.6)
    plt.legend()
    
    # Display the Plot Window
    plt.show()

if __name__ == "__main__":
    generate_damped_signal()

Docker and Docker Compose. Once you know that, you’ll be able to self host almost any FOSS.

Inkscape

I know you said software, but I would like to suggest a musical instrument. They still require learning a new language and typically provide a huge level of self satisfaction. A cheap keyboard or guitar can provide literally thousands of hours of study.

Slackware- Wait you said fun, nvm

Aseprite (you gotta compile it yourself if you wanna it free tho)

I’d say GIMP for photo editing would be a good one to learn. It’s come in handy in a pinch both at home and at work when I’ve needed something done up real quick.