Hello and welcome to the forum!
Duplicati does need to recreate the local database before you can do restores. This process shouldn’t take too long, but it can under some complicated circumstances. What version were you using before your disaster?
I am hardly an expert, but I have experimented with database recreation over the past year. Some older versions of Duplicati may not have written dindex files properly. When you recreate the database, Duplicati encounters these dindex files and decides it needs to read some or all of the dblocks (a very lengthy process) in order to rebuild the database.
There is a way to rewrite the dindex files without the corruption, but it requires an in-tact database. With recent canary versions this year, I have been able to fix my dindex files and then do a database recreation and have it complete in only 15 minutes or so on a 500GB backup.
In your case you may be forced to let the database recreation finish. If you go to About -> Show Log -> Live -> and choose Verbose in the dropdown, what does it show? You should see something like:
... processing blocklist volume X of Y
What do those numbers show?