Pruning keeps getting reenabled about gui

[BenWestgate]

Hi hebasto, a work around would be to put a bitcoin.conf file in /Volumes/Drive/Bitcoin with prune=0 BEFORE mounting your external drive, that way if it hasn't been mounted Bitcoin Core will not try to prune. This file will be buried and ignored after your external drive mounts.

Another work around would be adding -prune=0 to whatever method you are launching Bitcoin, be that command line or a .desktop file.

The file that remembers where your custom datadir is $HOME/.config/Bitcoin/Bitcoin-Qt.conf on linux.

Setting prune=0 in there however will be ignored on first launch, unfortunately this is probably a bug, since it DOESN'T ignore the datadir= entry.

The Welcome GUI overrides everything except the bitcoin.conf of the chosen datadir and the command line parameters. But it doesn't read the bitcoin.conf to know the prune setting to use until after the datadir is selected.

So the checkbox about pruning in that welcome screen will ONLY reflect the command line -prune=0 option given to bitcoin-qt.

You might also make the mount point read only after putting a bitcoin.conf in there then bitcoin will error out if your External Storage has not been mounted.

[BenWestgate]

Letting Bitcoin-Qt search for bitcoin.conf in $XDG_CONFIG_HOME/Bitcoin and reading it from your internal drive if present would resolve this issue. As is, bitcoin.conf is not read until after that choosedatadir window is dismissed.
bitcoin/bitcoin#16733