The Nextcloud Windows desktop client is very poorly written. We needed an in-house file hosting solution to replace really old Samba shares and Nextcloud seemed like a great option because we also were looking for a non-Google alternative to Google Docs/Drive (one of our clients has anti-Google policy).
After moving all files to Nextcloud server everyone (company of 20+ people) installed Nextcloud Windows Desktop client and connected to it with only virtual files option set (nothing is transfered until opened/edited). The initial "sync" after first seup took about 2-3 days to complete for everyone. Reason? Probably too many small files. The share contained about 300+GB of data in around 500k files (not sure about that number only a guess). Nextcloud checks every single file with server which computes hash for it which is stored locally. You can find threads on their community forum or reddit by people experiencing same slow behavior when they have a lot of small files. There were some promises from devs to resolve it with the latest client update but we didn't verify it yet.
After moving all files to Nextcloud server everyone (company of 20+ people) installed Nextcloud Windows Desktop client and connected to it with only virtual files option set (nothing is transfered until opened/edited). The initial "sync" after first seup took about 2-3 days to complete for everyone. Reason? Probably too many small files. The share contained about 300+GB of data in around 500k files (not sure about that number only a guess). Nextcloud checks every single file with server which computes hash for it which is stored locally. You can find threads on their community forum or reddit by people experiencing same slow behavior when they have a lot of small files. There were some promises from devs to resolve it with the latest client update but we didn't verify it yet.