There are threads saying that running in Terminal xattr -c /path/to/app will clear the flag.
Mixed feelings about this.
hey, why not, surely devs on Trilium are legit and it's just Apple bureaucracy
err, that's a slippery slope and the protection's are there for a purpose.
hmmm, are Trilium devs not committed enough to sign their apps properly (it's not difficult compared to the rest of their dev effort, jeez, even I have an Apple developer licence.
Going to take a timeout and just use the browser interface for now.