You can set new tab pages to open homepage. And set homepage to a local html file.

It also only supports one OS since like 2012 (at least in the past I could run the Windows release in Wine), which may seem like a weird complaint, but it sucks when I need to make sure our web page renders okay for the one business guy who uses Safari and I code on Arch. Thank God for Browserstack I guess.

Epiphany is what they call Safari on Linux: https://webkit.org/downloads :-). It's slow but works well for testing and debugging Safari-specific issues.

Safari and Epiphany are two completely different browsers.

Epiphany uses webkit, so it’s the same rendering engine.

Both being built on WebKit is different from both being the same browser, and even before the Blink split, behavior observed in Safari could differ from behavior observed in Chrome. Using observations of Epiphany as a proxy for Safari is just not reliable. I've seen differences between Epiphany and Safari without even trying—where it wasn't a matter of one being too outdated compared to the other.

Midori also uses WebKit.

What kind of custom new tab page are you talking about? Like a custom URL? Because that's possible.