ASUSWRT is built on a Linux kernel running a standard GNU/Linux toolset; but serious shortcomings. See below.
ALERT: Recommendation is to stay away, as security is taken very lightly.
Issues
Option issues:
Some options have hidden tooltips/help text. If you hover your mouse cursor on the option, but about 1/3 of options do not. So it is not obvious what some options provide.
Language Translation issues:
English translations are pretty shoddy in places.
For example: “Connect to DNS Server automatically” means “Overwrite the below DNS server settings with DNS servers broadcast by your ISP”.
If you switch between different languages – you might notice that some “dos” are translated as “don’ts” in other languages.
Not a sign of quality.
Keyboard issues:
You cannot copy-and-paste data to any input fields using the keyboard.
You also cannot undo using the good old Ctrl+Z.
DHCP issues:
Only supports up to 253 IP addresses for your local network.
This is new limitation, introduced retrospectively, meaning you can only delegate a single /24 subnet.
This limitation isn’t mentioned anywhere in the manual, product spec sheet, nor in marketing.
This limitation actually refers to an old limitation that has been in ASUSWRT since at least 2015 April and is not documented anywhere.
The /24 subnet limitation only applies to the Deep Package Inspection (DPI) tool that powers features like the Network Map, Network Analyzer, Quality-of-Service, and Bandwidth Monitor.
IPv6 issues:
Cannot configure the router to use an IPv6-only DNS server by setting an IPv6 address as the DNS server.
The back-end fully supports it, but the ASUSWRT web front end will only let you type in an IPv4 address.
Dynamic DNS issues:
Hard-coded against a list of 10 providers. No option to use something not on the list.
Cannot manually configure the web address of the service provider.
OpenVPN issues:
The .ovpn configuration profile sets the current external IP as the “remote” option even when a DynDNS hostname has been configured as a reliable way to reach the router.
This means the profile will stop working if your ISP assigns you a new IP address.
Deep Package Inspection issues:
To use any of these functions, you need to agree to a long-winded End-User License Agreement (EULA) from Trend Micro.
At the very bottom of the EULA, there is a section devoted to [the lack of] privacy.
The EULA also contains language holding the router’s owner responsible for notifying their friends, family, and house guests who connect to the internet through the ASUS router that any network activity may be recorded and shared with Trend Micro.
ASUSWRT will collect and transmit data about which websites you visit to Trend Micro, if you use any of the following features in ASUSWRT:
Apps/traffic Analysis
Bandwidth Monitor
Network Analyzer
Network Protection (AiProtection), blocks known malware domains
Parental Controls, including time scheduling
Quality-of-Service
Web History
Quality-of-Service (QoS) issues:
Early versions of ASUSWRT let users get in the thick of things and make manual adjustments to the QoS policies, and even let users create their own rules.
This feature has been removed in later updates, leaving some 540 predefined apps and services.
You can no longer manually prioritize any one service over others but are limited to sorting a list of generic categories including:
Gaming
VoIP
IM
Audio/Video Streaming
Web Surfing
File Transfers
Others. Almost every network enabled service that is not web browsing or a game from the early 2000’s will end up in the “Others” category.
Email issues:
Email notifications on parental control, or websites that are blocked requires your email to be hosted with either AOL, Google Mail, Tencent QQ, or 163.
It also requires you to save your email password in plain-text on the router and thus exposing it to anyone exploiting one of the many known remote access vulnerabilities.
The minute before midnight issue:
One minute to midnight every day, the router turns off a seemingly random set of features to observe a one-minute break from user demands.
The “URL Filter” firewall ruleset does not work during this last minute of the day.
The VPN service also kicks all clients at a minute to midnight.