Hello, please see here for the details I’ve collected as well, as I’ve run into this as well on a Raspberry Pi 4. My 4GB RAM is far from being full. No swap at all, I have it disabled.
This problem seems to be purely CPU-bound. Not RAM, and not disk-IO-bound. I’m watching what’s happening with both htop, and iotop. I tried migrating Mattermost’s data folder to a good-quality USB 3 stick, to split up the disk IO. That didn’t help at all.
I’m not running any additional Plugins beyond a basic install. No Clam-AV plugin.
I would sure appreciate a radio button somewhere in the System Console to make that image processing very lightweight, or not at all (as in, just attach the file, no matter what the file extension). Then let the web browser itself, or smartphone OS itself (with some Gallery-like app) show an image, using it’s own image-rendering ability (and the user must press the back button to go back to Mattermost).
I did my Mattermost install, using these (docker-avoiding) instructions. I’m on Raspbian Debian 10, with Mattermost 5.21, and MariaDB.