It’s dokuwiki.

If you want something that works very well and is quite convenient, I can recommend the Scaleway S3 Glacier storage. If you only need a few GBs, it will only cost a couple of cents per month.

If anything, I feel like Nextcloud Mail is the thing that’s going to end up being killed, not Roundcube. Nextcloud doesn’t exactly seem like a company that would buy a superior product just to kill it off.