Apple try to make it impossible to revert to a prior version of Safari Technology Preview (STP) – and they also try to force updates to the latest version immediately, without user consent. This is bafflingly hostile behaviour for what is supposed to be a beta version of the browser that users voluntarily, out of charity, help Apple debug.
It’s also highly problematic when new versions are flat-out broken. Starting with around STP 124 I started experiencing consistent crashes on some websites, making them completely unusable in STP. For the time-being I chose to use them separately in regular Safari, on the assumption that these egregious issues would be quickly fixed in the next STP version. Well, three versions later and those bugs have not been fixed. Not even close.
Now, with STP 126, it crashes on launch. Every time.
Well, thankfully there are places where you can obtain the prior versions, even if Apple won’t provide them. My preference is The Wayback Machine – you can start with this calendar, from which you can pick a date and (with any luck) the download page for that date will point to the version you want. You then download the disc image, delete the current copy of STP from your Applications folder (otherwise the pkg installer for the older version will refuse to work), and re-install the older version.
Once you’ve done that, make sure to turn Automatic Updates off in System Preferences, otherwise Apple will just trash your working version with the broken one again.
If you appreciate that – I certainly did; I like having a web browser that doesn’t crash on launch – remember that The Wayback Machine is run by the Internet Archive, a non-profit group, and they can always use monetary support as well as volunteers.
P.S. Yes, I’m aware that their donation page is sadly a bit janky. If you’re a web developer or designer, maybe you could volunteer some of your time to improve it? 😁