Without the linked PR, the GUI won't even let you sign the tx. (perhaps that should be changed but that's how it works atm)
I tried the latest master branch containing that PR but it can't seem to sign the lowest possible 0.1sat/vB transaction at first.
But after manually adding 1sat to the absolute fee, it let me sign the transaction.
Seem to be a minor issue with fee rate calculation since it's too small.
On a side note, since it's merged, we can expect this in the next release.
I'm currently installing my very first Electrum server, and figured I'd start a topic to keep track of my progress.
My goal is to create the first Electrum server that allows this.
Too bad (
a good thing actually now that there'll be 2),
electrum.labrie.ca beat you to it.