This is a list of all the open source software I have come across and use frequently to semi frequently. There will likely be some overlap with stuff everyone has already posted.

Photography and Image manipulation

• Darktable → RAW photo processing
• GIMP→ Photoshop alternative
• Krita → Digital painting (have only used it a bit, but I hear it’s good)
• Inkscape → Vector Graphics
• Automatic1111 → Diffusion model AI toolkit (mostly Stable Diffusion but also has extensions for other diffusion based models like OpenAI’s Shap-E)

3D modeling and Printing

• Blender → 3D Modeling, sculpting, 2D animation, compositing all rolled together (simply one of the best examples of FOSS)
• Meshroom → Photogrammetry
• PrusaSlicer → 3D printing slicer based on Slic3r

Video editing and Processing

• Kdenlive → Genuinely good video editor
• FFMPEG → Command line media toolkit (very complex but also works on android through Termux)
• Instant NeRF → Neural Radiance Fields, think photoscan to a 3D representation (not meant to make 3D meshes unfortunately)

Misc

• Calibre → E-book management
• Serge → Self hosted Local LLM’s made a bit easier to deal with
• Firefox → Web browser

FOSS I’m excited for

• DragGAN → Manipulate images by intuitively dragging, more on this here and here (official code being released this month but there are already projects based on the paper with working examples)
• CoDi → “Composable Diffusion” Any2Any conversion Txt2Vid, Vid2Audio, Audio+Txt2Img, whatever
• Neuralangelo → Promises to be NeRF’s for 3D models (don’t know if it will be FOSS but I’m hopeful)

My last experience with Win10 vs now:

(FOSS in bold)

• Edge -> LibreWolf, Brave
• Windows Mail & Calendar -> Thunderbird, Tutanota
• Windows Explorer -> Thunar, PCManFM
• Todoist/iCal -> fruux + Thunderbird
• NCH VideoPad -> Kdenlive
• iTunes, Spotify -> CDs, Audacious, DeaDBeeF, Bandcamp
• VLC -> mpv, Parole
• OneNote -> Obsidian Joplin + Backblaze B2
• Firefox Lockwise -> Bitwarden
• WPS Office -> LibreOffice, ONLYOFFICE
• VSCode -> Micro
• Visual Studio -> Micro + GCC + Glade
• Finale -> MuseScore
• NT -> Linux (obviously)
• Windows 10 -> Debian, Arch Linux

And now, the online services:

• Ecosia -> LibreX
• YouTube -> CloudTube
• Twitter -> Mastodon
• Reddit -> Libreddit, Lemmy
• Dropbox, Google Drive -> MEGA, Filen, USB sticks
• Blogger -> Neocities, Flounder (gemini protocol)

Sorry for the long post. Here are some potatoes:

I recommend https://alternativeto.net/ since you just type in the software name and it will show alternatives rated by popularity. You can filter by many things including “open source”.

• Inkscape as well for all of the Adobe stuff
• Pandoc and Pympress for all my presentations
• Claws Email
• Khard + Khal + todoman + vdirsyncer for the rest of the PIM stuff
• Zathura is my PDF reader
• Syncthing replaced GDrive more or less
• qutebrowser

I switched to Linux in 2006.

Calibre is excellent for ebook management. If you are just using it to sync with your ereader you might be able to do without. I have a Kobo and use Calibre but will likely stop doing that because there are now tools that are a lot lighter to convert epub to kepub and add covers, etc.

I keep a list of software I like to use, I need to update it.

What distro did you choose?

CMUS as a music player. Clean interface, lightning fast and plays anything. I use it daily.

I think most of them I’d be using on windows as well. Like blender, gimp, krita, librewolf, libreoffice, thunderbird, virtualbox, etc… etc… etc… Although it was 15 years ago I had switched to mostly open source applications in the years prior to eventually switching to linux entirely.

Linux, to replace Windows :p

Check out KDE Connect / gsConnect for integration your phone to your computer. It can sync notifications, messages, share clipboard, media playback controls, use either device as mouse/keyboard for the other. Its really good on Android. For iOS the app is much newer and with limited features due to iOS limitations

If you’re on KDE, something as ‘basic’ as the file manager Dolphin feels decades ahead of the Windows File Explorer

Zim Desktop wiki is really good for creating a personal wiki. Think building a personal knowledge base or notebook with interlinked articles

@Witch
A helpful browser extension tool is Privacy Redirect. It allows automatic link redirects from:

Reddit -> Libreddit
Youtube -> Invidious
Google -> Startpage (or other)
Maps -> OpenStreetMap

… and a few others.
It is very customizable for what instances or sites you need which is why I think it’s great.

LibreOffice (and not OpenOffice) is a must.

I have tried really hard to make the switch to GIMP, but Photoshop is too engraved within me.

I will probably keep using Photopea instead.

Not a replacement per se, but I am just amazed by how much better some common FOSS apps feel in Linux compared to Windows. Apps like VLC, Calibre, FreeCAD, Libreoffice, hell even Firefox are so much smoother in a UNIX system, almost like THIS is their real home!

Calibre is very powerful for book management, you should stick with it.

I love Notepad++. I use notepad apps way more than I should, but I really prefer the lightweight, no formatting text editing experience. It’s lightweight and can be installed as a portable version and supports all kinds of languages and plugins.

Edit: I suppose this isn’t in the spirit of the question though since Notepad++ is not for Linux. Still it’s an alternative to a Windows program that’s FOSS. (2/3 on topic)

I’ve never heard of Logseq. But I use an obsidian alternative called trilium. I’ll give logseq a shot.

I will say, despite how old and outdated calibre looks, it’s an absolute beast and contains every feature you would need. I use it to tag all my pdfs with the correct book information (which calibre with find for you) and use it to export my books into a specific folder hierarchy for easy browsing using KOReader on my Kobo e-reader (which runs on linux!)