[odamizu]

Thank you, KevinH. As you predicted, zsh worked find to unpack Sigil's .txz (and also run epubcheck.jar and kindlegen from the command line).

What was surprising, though, is I accidentally double-clicked Sigil's .txz file, and Catalina's default Archive Utility unpacked it just fine. So Terminal command is not necessary in Catalina. (I tested it both ways — tar -xvf on Terminal and simply double-clicking the .txz file. Both worked.)

Launching Sigil the first time (I did a clean install) resulted in a pop-up that says, Sigil can't be opened because Apple cannot check it for malicious software. This software needs to be updated. Contact the developer for more information. It then offers two buttons: Show in Finder and Okay. If, instead, you right-click-Open, you get three choices: Show in Finder, Okay and Open. Clicking Open launches Sigil, no problem. You can also go to System Prefs > Security after the initial launch attempt and there will be a message saying, Sigil was blocked from use because it is not from an identified developer with a button to Open Anyway. This message is a bit off-putting since Sigil is code-signed (confirmed with spctl -a -v).

For unsigned & unnotarized apps, like the KindleUnpack applet, you get a pop-up that says, macOS cannot verify the developer of KindleUnpack 64 v0.81. Are you sure you want to open it? By opening this app, you will be overriding system security which can expose your computer and personal information to malware that may harm your Mac or compromise your privacy. Once again you can override Gatekeeper with right-click-Open or System Prefs > Security.

Interestingly, some unsigned/unnotarized apps (like Alf's standalone app) won't open at all if unzipped in Catalina, but will open if you unzip it on Mojave or High Sierra then copy it over to Catalina.

Command line tools (like Kindlegen and epubcheck) run without any warning.

Some notarized apps (like BBEdit) pop-up a milder warning: BBEdit is an app downloaded from the Internet. Are you sure you want to open it? But other notarized apps (like KindlePreviewer and Send to Kindle) launch without any warning at all.

I then did some very quick tests on plugins, all of which worked (after installing ActiveTcl). These include: EpubCheck, cssRemoveUnusedSelectors, ePub3-itizer, TagMechanic, KindleImport, KindleGen, PunctuationSmarten, ShowSemantics, etc.

I will spend more time with Sigil on Catalina in the coming days and report back anything interesting, but so far so good.

I have also spent a tiny amount of time on Calibre 3.48 and plan to install 4.2 once I get a chance.