List of Personal Knowledge Management Systems

Below taken from the subreddit. Link

Methodologies

Abbreviation:What it means:
FOSSFree and open-source software
FreeEverything that is part of the app is free
Free +$Free, but has additional paid features
PaidMost or all features are paid
+ n.desktopwith native desktop app
nn.non-native
W/M/LWindows/Mac/Linux
iOS/AiOS/Android
BDLBidirectional linking
LinksRegular links between notes

Side note 1: Apps that have both web & native apps are under "Web-based applications" and are specified accordingly, however, only native apps are under "Native applications".

Side note 2: Native apps assume local storage unless otherwise stated.

Side note 3: If there's a question mark somewhere, it means that I'm not sure. If you know what correctly belongs there, I'd appreciate it if you let me know in the comments. Thanks.