Semmelstulle on Nostr: I tried it using Brave, too. Later AltStore added on Mastodon that this must be done ...

I tried it using Brave, too. Later AltStore added on Mastodon that this must be done through Safari, but after inserting my mail address again I did not have to buy again. It just offered me the download link.
Though I feel like Apple made the process clunky on purpose.
Tap link, get Pop-Up, go to settings, tap link again and then maybe it starts installing (for me after toggling off WiFi, mobile data on, mobile data off again and then WiFi on again).