There are many resources across depending on what you are looking for: https://switching.software https://madaidans-insecurities.github.io https://www.btw.so/open-source-alternatives https://gitea.it/devol/Awesome-Privacy-servizi-web-open-source https://github.com/lissy93/awesome-privacy

Please note that these list may not be completely up-to-date, but you find and a lot of useful tools there imho.