Many FOLIO recordings and presentations are available at the Open Library Foundation video YouTube channel (sorted by most recent). These include FOLIO Forums, monthly Sprint Reviews, and various special topics.
One recent example
Some other presentations (sorted by most recent). Note that some might be out-of-date and maybe still useful.
- Stripes overview presentation conducted by John Coburn to introduce the folijet EPAM team. Onboarding overview of Stripes, the front-end framework of FOLIO. The accompanying slides. (2018 August)