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Dropbox-Uploader
Dropbox Uploader is a BASH script which can be used to upload, download, list or delete files from Dropbox, an online file sharing, synchronization and backup service.
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InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
I use this on MacOS/Linux to upload my vaults without having the official Dropbox app installed - https://github.com/andreafabrizi/Dropbox-Uploader
Nevertheless, the site you mentioned does also recommend https://syncthing.net/ as file-sync tool, and this tool seems to work with Dropbox as well. So, since you value the advice of this site, you should give it a try. (cannot say anything about this app as I do not use it).