For me: Wezterm. It does pretty much everything. I don’t think Alacritty/Kitty etc. offer anything over it for my usage, and the developer is a pleasure to engage with.
Second place is Konsole – it does a lot, is easy to configure, and obviously integrates nicely with KDE apps.
Honorable mention is Extraterm, which has been working on cool features for a long time, and is now Qt based.
Just note that the comment was inaccurate, in that their weird encryption is indeed open source at least.
Ah yes you can tell by the post title: