> I doubt donations to MZLA Technologies Corporation will reach the Thunderbird project in any meaningful way.

You are basing this statement on what data?

https://www.thunderbird.net/en-US/donate is managed by MZLA, it has one open source product, Thunderbird. We pay a required Thunderbird trademark fee to the Mozilla Foundation and little more than that, which is captured in https://stats.thunderbird.net/#financials.