One thing I do remember is Ryan explaining how just being willing to directly ask people for money has been surprisingly effective.

It's also worth putting Thunderbird's relationship to Mozilla in proper perspective: for all intents and purposes, Thunderbird is a completely independent project. Since 2017 (https://blog.thunderbird.net/2017/05/thunderbirds-future-hom...), the Mozilla Foundation has primarily acted as Thunderbird's fiscal home, providing support for donations / bookkeeping / taxes / legal matters much in the same way that the Software Freedom Conservancy hosts Git, Homebrew, Inkscape and others, or how Software in the Public Interest hosts PostgreSQL, systemd, Xorg, FFmpeg, 0 A.D, and more.

If I understand last year's MZLA Technologies announcement correctly (https://blog.thunderbird.net/2020/01/thunderbirds-new-home/), it sounds similar to the split between the Mozilla Foundation and the Mozilla Corporation, where the former is a legal non-profit and the latter entity is for-profit and able to enter into commercial, revenue-generating agreements, but still wholly owned by the non-profit Foundation.

...But you should really listen to the podcast, I could be getting all of this wildly wrong.