Newer, more feature-rich, and currently updated replace for Ubooquity, which was last updated in 2018. Also, Ubooquity’s best Android reader (Kuboo) is no longer supported either and is in archive mode by the dev.
Komga does more and has an officially supported plugin for Tachiyomi on Android, which is considered to be a great manga/comic reader, also currently maintained.
The official Docker image for Komga doesn’t allow for UID/GID settings, nor timezone via environment variables, thus causing issues on some devices with file permissions (e.g. Synology).