Marcus Müller’s answer shows how to get version information for any distribution release or container image.
For Debian (and Ubuntu), you can use rmadison instead (in the devscripts package):
$ rmadison qemu
qemu | 1:5.2+dfsg-11+deb11u3 | oldoldstable | source, amd64, arm64, armhf, i386
qemu | 1:5.2+dfsg-11+deb11u3 | oldoldstable-debug | source
qemu | 1:7.2+dfsg-7+deb12u16 | oldstable | source
qemu | 1:7.2+dfsg-7+deb12u16 | oldstable-debug | source
qemu | 1:7.2+dfsg-7+deb12u16 | oldstable-proposed-updates-debug | source
qemu | 1:7.2+dfsg-7+deb12u17 | buildd-oldstable-proposed-updates | source
qemu | 1:7.2+dfsg-7+deb12u17 | oldstable-proposed-updates | source
qemu | 1:7.2+dfsg-7+deb12u17 | oldstable-proposed-updates-debug | source
qemu | 1:10.0.2+ds-2+deb13u1~bpo12+1 | oldstable-backports | source
qemu | 1:10.0.2+ds-2+deb13u1~bpo12+1 | oldstable-backports-debug | source
qemu | 1:10.0.6+ds-0+deb13u2 | stable | source
qemu | 1:10.0.6+ds-0+deb13u2 | stable-debug | source
qemu | 1:10.0.6+ds-0+deb13u2 | unstable | source
qemu | 1:10.1.2+ds-1 | testing | source
qemu | 1:10.1.2+ds-3 | unstable | source
qemu | 1:10.1.2+ds-3 | unstable-debug | source
qemu | 1:10.2.0~rc1+ds-1 | experimental | source
qemu | 1:10.2.0~rc1+ds-1 | experimental-debug | source
On a Debian system (or similar), this will show results for currently-supported releases of Debian by default; on a Ubuntu system (or derivative), it will show results for Ubuntu. The -u option can be used to switch sources (-u debian or -u ubuntu).
One benefit of this approach is that it shows all available versions, including backports, regardless of the repositories configured on the querying system or in the container image.
For Debian specifically, you can get information on older releases as well by querying the archived releases instead:
$ rmadison -u archive qemu
qemu | 0.6.1+20050407-1sarge1 | debian/sarge | i386, powerpc
qemu | 0.6.1+20050407-1sarge1 | debian/sarge-security | source, i386, powerpc
qemu | 0.8.2-4 | debian/etch-m68k | source
qemu | 0.8.2-4etch3 | debian/etch | source, amd64, i386, powerpc
qemu | 0.8.2-4etch3 | debian/etch-security | source, amd64, i386, powerpc
qemu | 0.9.1-10lenny1~bpo40+1 | debian/etch-backports | source, amd64, i386, powerpc, sparc
qemu | 0.9.1-10lenny1 | debian/lenny | source, amd64, i386, powerpc, sparc
qemu | 0.9.1-10lenny1 | debian/lenny-security | source, amd64, i386, powerpc, sparc
qemu | 0.12.5+dfsg-3squeeze4 | debian/squeeze | source, amd64, armel, i386, kfreebsd-amd64, kfreebsd-i386, mips, mipsel, powerpc, sparc
qemu | 0.12.5+dfsg-3squeeze4 | debian/squeeze-security | source, amd64, armel, i386, kfreebsd-amd64, kfreebsd-i386, mips, mipsel, powerpc, sparc
qemu | 0.12.5+dfsg-3squeeze5 | debian/squeeze-lts | source, amd64, i386
qemu | 1.1.2+dfsg-2~bpo60+1 | debian/squeeze-backports | source, armel, ia64, kfreebsd-amd64, kfreebsd-i386, mips, powerpc
qemu | 1.1.2+dfsg-6a+deb7u7~bpo60+1 | debian/squeeze-backports | source, amd64, i386, mipsel, sparc
qemu | 1.1.2+dfsg-6a+deb7u12 | debian/wheezy | source, amd64, armel, armhf, i386, ia64, kfreebsd-amd64, kfreebsd-i386, mips, mipsel, powerpc, s390x, sparc
qemu | 1.1.2+dfsg-6+deb7u25 | debian/wheezy-security | source, amd64, armel, armhf, i386
qemu | 2.0.0+dfsg-4~bpo70+1 | debian/wheezy-backports | source, s390x
qemu | 2.1+dfsg-5~bpo70+1 | debian/wheezy-backports | source, sparc
qemu | 1:2.1+dfsg-11 | debian/jessie-kfreebsd | source, kfreebsd-amd64, kfreebsd-i386
qemu | 1:2.1+dfsg-12+deb8u5a~bpo70+1 | debian/wheezy-backports | source, amd64, armel, armhf, i386, ia64, kfreebsd-amd64, kfreebsd-i386, mips, mipsel, powerpc
qemu | 1:2.1+dfsg-12+deb8u6 | debian/jessie | source, amd64, arm64, armel, armhf, i386, mips, mipsel, powerpc, ppc64el, s390x
qemu | 1:2.1+dfsg-12+deb8u15 | debian/jessie-security | source, amd64, armel, armhf, i386
qemu | 1:2.8+dfsg-3~bpo8+1 | debian/jessie-backports | source, amd64, arm64, armel, armhf, i386, mips, mipsel, powerpc, ppc64el, s390x
qemu | 1:2.8+dfsg-6+deb9u9 | debian/stretch | source, amd64, arm64, armel, armhf, i386, mips, mipsel, ppc64el, s390x
qemu | 1:2.8+dfsg-6+deb9u17 | debian/stretch-security | source, amd64, arm64, armel, armhf, i386
qemu | 1:3.1+dfsg-8+deb10u8 | debian/buster | source, amd64, arm64, armel, armhf, i386, mips, mips64el, mipsel, ppc64el, s390x
qemu | 1:3.1+dfsg-8+deb10u12 | debian/buster-security | source, amd64, arm64, armhf, i386
qemu | 1:5.2+dfsg-9~bpo10+1 | debian/buster-backports | source, amd64, arm64, armel, armhf, i386, mips64el, mipsel, ppc64el, s390x
qemu | 1:5.2+dfsg-11+deb11u3 | debian/bullseye | source, amd64, arm64, armel, armhf, i386, mips64el, mipsel, ppc64el, s390x
qemu | 1:7.2+dfsg-7+deb12u2~bpo11+1 | debian/bullseye-backports | source
The UDD can also be used as a source:
$ rmadison -u udd qemu
qemu | 1:5.2+dfsg-11+deb11u3 | bullseye | source, amd64, arm64, armhf, i386
qemu | 1:5.2+dfsg-11+deb11u5 | bullseye-security | source, amd64, arm64, armhf, i386
qemu | 1:7.2+dfsg-7+deb12u15 | bookworm-security | source
qemu | 1:7.2+dfsg-7+deb12u16 | bookworm | source
qemu | 1:7.2+dfsg-7+deb12u17 | bookworm-p-u | source
qemu | 1:10.0.2+ds-2+deb13u1~bpo12+1 | bookworm-backports | source
qemu | 1:10.0.2+ds-2+deb13u1 | trixie-security | source
qemu | 1:10.0.6+ds-0+deb13u2 | trixie | source
qemu | 1:10.0.6+ds-0+deb13u2 | sid | source
qemu | 1:10.1.2+ds-1 | forky | source
qemu | 1:10.1.2+ds-3 | sid | source
qemu | 1:10.2.0~rc1+ds-1 | experimental | source