Finally. Armory was ready to build the database, organize blockchain and scan transaction history.
I was able to see my balance but "node ofline".
Now I started bitcoin core in paralell.
Armory went online and it shows green "connected" in the status bar. I could not be more happy.

So now I tried to get to stage 2. Sending my BTC out of this wallet.

Beeing in "advanced user" GUI I tried to "send bitcoins".
I entered the SegWit address of my trezor as recipient.
I left all settings to be default and adjusted the fee to be generous 15 sat/B (conservative auto gave 6.5 sat/B and trezor currently defaults to 8 sat/B for a "high" fee transaction).

Then I sent the whole amount unlocking the wallet.

5 seconds of nothing happening, then an error popup "The transaction that you just attempted to broadcast has failed with the following error: missing inputs"!

Is it safe to paste the armorylog.txt output on this?