Your /tmp is currently in RAM to prevent the SDcard from being hit hard, this is good for the SDcard, but if your RAM is not very large then exceeding RAM size will result in issues so you have a choice to make, get a device with more RAM and continue running from the SD card, use an SSD or use the SD card in the knowledge that failure rate will be high and prepare for that (regular backups which you should anyhow do etc).
That makes this /tmp patch even less desirable. I don’t want my Nextcloud unit to become the “old lady who swallowed a fly,” where a “fix” can become an even bigger problem later, and doesn’t even address the cause of the problem.
The Odroid device I have it installed on has 2GB of RAM, and as I said, everything worked fine until I started a series of updates back in October or November. I stopped that when errors showed up. I don’t think that the RAM size is being exceeded in trying to do system updates; I think there’s a bug in the system that is making it look like it’s being exceeded.
Do the devs ever read these posts? I would think that this might be something they would want to know about, and to fix. This is really getting frustrating. Thank you.
Your RAM is 2GiB, your /tmp lives is RAM you can’t have anything larger than 2GiB (and realistically even less due to OS overhead etc.) pass through /tmp, you can choose to move /tmp to your SDcard thus allowing larger files (though still limited since your SDcard is only 32GB) but at the same time shortening the life of the card and also allowing /tmp filling up to stop your whole system.
As for the update have you tried to run it from CLI to see what happens?
(for me that would be sudo -u www-data php --define apc.enable_cli=1 /nextcloud/updater/updater.phar for you probably a different path and no need for the apc bit)
/Edit - you should probably focus on one issue, my personal guess would be get the update finished first.