Thanks, yet it is not in my 20.12.2
THis may be available to me:
$ rmadison dolphin
dolphin | 4:18.08.0-1 | oldoldstable | source, amd64, arm64, armel, armhf, i386, mips, mips64el, mipsel, ppc64el, s390x
dolphin | 4:20.12.2-1 | oldstable | source, amd64, arm64, armel, armhf, i386, mips64el, mipsel, ppc64el, s390x
dolphin | 4:22.12.3-1 | stable | source, amd64, arm64, armel, armhf, i386, mips64el, mipsel, ppc64el, s390x
dolphin | 4:23.08.1-1 | testing | source, amd64, arm64, armel, armhf, i386, mips64el, ppc64el, s390x
dolphin | 4:23.08.1-1 | unstable | source, amd64, arm64, armel, armhf, i386, mips64el, ppc64el, riscv64, s390x
dolphin | 4:23.08.1-1 | unstable-debug | source
but I was told not to cause Frankenstein version of the Debian by mixing repos…
$ sudo apt install dolphin -t bullseye-backports
dolphin is already the newest version (4:20.12.2-1).