The latest version of Electrum is running on windows 10.

Receiving BTC, no problem.

Opening Lightning channel.

I used the suggested one and have now:

Node alias: there be dragons here

Local: 5 mBTC
Remote: 0 mBTC
Status:OPEN

Channel Details:

Capacity 5 mBTC
Can send: 4.04586 MBT
Can receive: 0mBTC

In my understanding, all looks fine.

My first send was 0.5 mBTC to BLW, connected to ACINQ, failed. QR code was created with BLW.

The second send was 1 mBTC to BlueWallet, which failed. QR code was created with BlueWallet. (edit: BLW to BlueWallet)

BLW and BlueWallet are active wallets.

What can be a possible solution?

It can be that the suggested node gives routing problems? Is it possible to check this?