Nice site, but better is AlternativeTo, there are a lot more. You can add it to your search engines of your browser.
https://alternativeto.net/browse/search?q=%s
Although, I have found a lot of cases on there advertised as FOSS, when in reality they are proprietary.
Yes, but not the case here. There are other online services which are FOSS, but hosted in sites which are not, but Teknik isn’t hosted in a cloud service, it’s based on blockchain, but if you want, you can host it yourself. Apart I use also GoFile not for storing, but for sharing some files, where it isn’t so important that other can see it , it’s free but not FOSS but a very good service, anyway better than DropBox (no account needed to use it)., with good privacy, security and own virus scan… Similar is https://download.gg/en/ (French service)