I tried to download an ofline copy from https://tiddlywiki.com/upgrade.html with Vivaldi 7.0.3505.7 on MIUI (Android). It got stuck in a loop and ultimately the browser reported a server error. However I ended with three similar ~75KB files named ‘TiddlyWiki Upgrader — upgrade your files to the latest version’ in my Downloads folder. I have uploaded one of them here https://dpaste.org/YNGGA
I can’t reproduce it with Firefox 126.0.1 on same OS. It reports downloading a 6.5MB file (yet the downloaded upgrade.html file is about 21MB big). No feedback about using it yet, I’ll have to proceed carefully.