Hope this is not Raspi?
What is wrong with RPi? I thought RPi 4 for two calendars (one calendar per user) on nextcloud would be plenty, looking at the requirements:
A 64-bit CPU, OS and PHP is required for Nextcloud to run well. …
Nextcloud needs a minimum of 128MB RAM per process, and we recommend a minimum of 512MB RAM per process.
Also, how resource intensive could/should be syncing two personal calendars (via Thunderbird)? I don’t understand, why NextCloud with this virtually negligible task struggles so much. The pi has 7+GB of free memory, CPU load under few %, rarely one core has some load, most of the time nothing accesses the card nor disk (virtually 0 iowait; only with a short spike once every 5 minutes). Why does Nextcloud take half a minute to several minutes for a sync of one calendar in Thunderbird?
I see 1.8GHz in glances (in my case actively cooled, but since it doesn’t seem to max any core, it probably doesn’t matter). I have other RPi4s, I wonder why is backend in Java (well, Scala) ok, backend in Haskell ok, but backend in PHP wouldn’t be? I still don’t understand how Nextcloud can lock up for so long (tens of seconds) on a simple write event into calendar operation. That hacky unoptimized Java BE which does joins manually and inserts sequentially (so from a db perspective just awful), handles 5-10 times more data and still does it order of magnitude faster. My old phone which was weaker than even RPi4 could handle dozens of such small operations in one second (I believe that was SQLite + Java). There must something seriously wrong with Nextcloud (including PHP runtime) and/or the RPi, because such insignificant amount of data (1 word title, one date, one reminder option), most likely merely few dozens of bytes, takes so incredibly long to process and write to db…