

Kakao nuked the official Tachiyomi Extension repo because they “infringe on their copyright”.
The Extension repo does not and never has offered copyrighted material, it merely facilitated access to sites that do within Tachiyomi. Essentially it was a collection of hyper specific Browsers. The repo is gone, the extensions are not (they are now in a different repo provided by a user). Tachiyomi itself allows for 3rd party repos now and everyone is mad at Kakao for making the App less usable.
For now it should work but it will have an increasing likelihood of breaking with every future Android Update.
Migrating to Mihon now is recommended, one of the devs worked on Tachiyomi and for now the code is almost identical which allows easy migration via a Tachiyomi Backup.
Migrating in the future might be more difficult because incompatibility between Tachiyomi and future versions of Mihon could mean Backups from Tachiyomi cannot be restored by Mihon.