When comparing Let's Chat vs Mattermost, the Slant community recommends Mattermost for most people. In the question“What are the best on-site Slack alternatives?” Mattermost is ranked 4th while Let's Chat is ranked 17th. The most important reason people chose Mattermost is:
You don't need to rely on someone else's servers, you can host Mattermost on your own server.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Free and open source
Let's Chat is available for free. It's licensed under the MIT license with source code available on GitHub.
Pro Can be self-hosted
You don't need to rely on someone else's servers, you can host Mattermost on your own server.
Pro One-line Docker install
With Docker set up, you can install Mattermost with the following command:
docker run --name mattermost-dev -d --publish 8065:80 mattermost/platform
For other cases, installation instructions can be found here.
Pro Similar to Slack
Almost all features of Slack are available in Mattermost.
Pro Free - OpenSource
You can download and use it as free for self-hosted server.
Pro Mobile apps for android and iOS
Pro You can change theme
Pro Desktop app for MacOS, Linux and Windows
Pro Browser notifications
Pro Mark-Down support
Yes, it supports markdown.
Cons
Con No 1:1 direct messages via webclient
The ability to directly message other users is still being implemented.
Con No easy End-to-End Encryption setup
Con Features not available out of the box
Difficult to setup the many features it offers. The easy docker installation is for the application only, not it's feature sets. Requires a license for full-set of features.
Con Centralized
Con Poorly made iOS app
Built natively using React it suffers from unresponsiveness, input lag, and sometimes broken services. Coupled with a bad user experience.
Con Poorly made Android app
The Android application is just a badly wrapped web-view which does not perform well and has no form of offline caching whatsoever.
Con Self-Hosted
This doesn't work for every type of company. Mainly great for those concerned with privacy, security, compliance and control of your data/information.