@scattergather@tek@moshidon@apps I managed to temp fix the Official Mastodon app by manually installing the cert for Sectigo [1] waiting for tusky update to get pushed to f-droid. My fix doesn't help with fedilab but since it fixed the official Mastodon app maybe it will work for moshidon.
@scattergather I'd gotten a report from @SnazzyGumball about the same with Tusky. The root cause is that I recently updated the SSL cert (which expires yearly), and now it's signed with a root cert newer than older versions of Android support. Tusky is fixing this by bundling the root cert with their app.
BTW, we're using Sectigo, which has about a 25% SSL CA market share. I mention that just to point out it's not a local weirdness thing, but a widespread issue.